Available online on 15.09.2022 at http://jddtonline.info

Journal of Drug Delivery and Therapeutics

Open Access to Pharmaceutical and Medical Research

Copyright  © 2022 The  Author(s): This is an open-access article distributed under the terms of the CC BY-NC 4.0 which permits unrestricted use, distribution, and reproduction in any medium for non-commercial use provided the original author and source are credited

Open Access  Full Text Article                                                                                                                                                                                           Research Article 

Assessment of resilience of aromatic plants during the COVID-19 pandemic in Douala, Cameroon

Patrice Brice Mvogo Ottou¹, Christian Wilson Saagu Fogang¹, Zenabou Ndiang¹, Jacques Bruno Ngotta Biyon¹, Seraphine Ebenye Mokake¹, Fidèle Bemadoum Mbezo², Jean Lagarde Betti^1,3, Din Ndongo¹, Richard Jules Priso¹*

¹ Biology and Physiology Laboratory of Plant Sciences, Faculty of Sciences, University of Douala, PO Box. 24157 Douala, Cameroon

² Laboratory of Microbiology, Faculty of Science, University of Yaoundé I, PO Box. 812 Yaoundé, Cameroon

³ Cameroon National Herbarium, PO Box. 812 Yaoundé, Cameroon

INTRODUCTION

The Cameroonian flora abounds in an important reserve of plants with edible, ornamental and medical characters estimated at more than 8500 species ¹. Apart from cultivated species, several lesser known wild species have great cultural importance and strong economic potential for food, care, energy, clothing and housing construction ^2-3 Medicinal species represent a cultural heritage in developing countries and an invaluable resource for the pharmaceutical industry ⁴. While it is true that plants have long been used in herbal medicine, their renewed interest among the public has been felt more during pandemic such as the Covid-19 pandemic. This specific interest obeys to the non-acceptance of pharmaceutical products and also to their high cost by population.

With the first contamination cases and the confinement recorded by March 29, 2020, population started to prepare themselves for preventive and curative measures to deal with the Covid-19. Actors of traditional medicine consequently got down to search plants as solutions to avoid the worst of the Covid-19 pandemic. Many herbal therapeutic protocols have therefore been put in place ^5-6. Following this, many habits, both dietary and therapeutic, involving plants have emerged, becoming a lifestyle and dietary rules. Spices, vegetables, and fruits were used for this goal. Aromatic plants formerly considered underused and neglected species have been given special attention.

Aromatic plants are ordinarily consumed for culinary and dietary uses due to their aromas as well as their essential oils and various bioactive metabolites for medicinal purposes ^7-8-9. In line with this, Kuete-Sezine et al. reported that Cameroonians relied on traditional medicine to counteract the Covid-19 pandemic ⁶. Essential oil and phenolic compounds highlight the greatest interest of these plants such as in their abilities to inhibit oxidative reactions and the growth of many microrganisms ^8-10.  These findings point to the aromatic plants as a therapeutic alternative for pharmaceutical products. Moreover, aromatic plants offer real opportunities for socio-economic development of farmers and neighbouring population to improve their incomes ⁷. These plants constitute the main part of the therapeutic arsenal used by traditional healers to treat many diseases ¹¹. 

However, the lack of adequate scientific knowledge and management structures adapted to aromatic plants can lead to the endogenous treatment of the Covid-19 disease. On one hand, traditional healers operate usually alone and out of the scientific system without clear protocols that can be followed or repeated elsewhere. Each of them proposes its own protocols including the same or different plants. Secondly, cultural culinary habits are dominantly based on the common consumption of aromatic plants for their taste, easiest digestion and therapeutic values. The population consumes these plants usually without any perfect knowledge of their scientific components and effects. The pandemic due to the Covid-19 was associated with the denial by population to consume pharmaceutical drugs following various comments on their lethal capacities. The overall pauperisation of the population and the lack of insurance in Cameroon to take care of patients with the Corona virus constituted another obstacle to accessing the health system which itself is poorly equipped.

Most Cameroonian population, such as those of Douala IV sub-division, went back to the popular knowledge of the medicinal outcomes of aromatic plants and succeeded in facing this pandemic. The main objective of this study is to determine different bioactive compounds of aromatic plants used by the population of Douala IV sub-division.

MATERIAL AND METHODS 

Douala IV sub-division is one of the urban Douala town that is composed of six urban sub-division municipalities, (Douala I, Douala II, III, IV, V, VI). It combines the urban and rural area with Bonassama as the headquarters. It is bounded to the north by the Moungo sub-division, to the South and East by the Wouri River and to the West by the Fako Division (Figure 1). Douala IV extends on 3.500 km² and host about 395.536 inhabitants in 2019 with as main neighbourhoods and villages, Bonamatoumbe, Bonendale and Bwadibo which chosen for this study on the basis of the scarcity of public and private health structures and also in the objective to complete an ethnobotanical study on medicinal flora.

Figure 1: The study site for the ethnobotanical surveys

Ethnobotanical survey 

We surveyed between September and December 2020, the Bonendale, Bonamatoumbe and Bwadibo villages in the Douala IV sub-division with the objective to assess on the base of the socio-demographic and cultural information of the respondents, information on traditional pharmacopoeia from the population on aromatic plants used to treat different diseases by the local population during confinement. The method consisted of interviewing in French and/or local languages (Bassa, Douala, Bamileke, Ewondo), the population about popular use of medicinal plants ¹². For each therapeutic indication, details of the recipe were carefully noted and the plant was filmed and harvested. This collection was facilitated by guides chosen from informants in each neighbourhood to facilitate the identification of species in situ. For each plant cited as aromatic, we noted the plant part used, the mode of preparation, the pharmaceutical form, the mode of administration, the places of supply, other uses, their availability or not as well as the harvesting methods practiced. Samples of aromatic plants were collected and identified at the Cameroon National Herbarium. Information on diseases and symptoms or physiological effects were collected from nurses and health workers in the Bonassama health district and supplemented by a bibliographic review ^12-13. For practical use of the data and harmonization with the international system, the health problems have been grouped into major groups of diseases according to the latest classification of diseases proposed by the World Health Organization WHO (1996; 2001) and adopted by the Organization of African Unity (OAU) for the Cameroon pharmacopoeia ¹³.

Assessment of use value and cultural significance

Among multiple indices used in quantitative ethnobotany to assess the importance of a species ¹⁴, we retained for the identification of aromatic plants with pharmaceutical interests:

- the contribution of each plant in the constitution of recipes (Cpr) as seen by Dassou et al. ¹⁵ calculated according to the formula: 

Cpr = Nr/Nt×100                              (1)

where Nr is the number of recipes requesting the plant and Nt, the total number of recipes;

- the frequencies of citations of the different plants were determined according to the formula:

Fc = Nc/N                                           (2)

where Nc is the number of citations of the plant and N the total number of citations of aromatic plants listed;

- the therapeutic use value (VUT) of each species was calculated using the following formula:

VUT = U/Nenq                (3)

where U is the number of uses where the species is mentioned by each informant and Nenq, the number of informants who mentioned the species determining the significant use value of an aromatic plant in a given environment compared to others;

- the performance index (Ip) described by Betti ¹ that represents the efficiency of a plant by pathology among all the registered pathologies that mention the plant in question according to the following difference:

IP = (Nc/N) – (Ncm/Nt)                 (4)

where Nc is the number of citations of a plant in the treatment of a disease; N: the total number of citations of all plants used in the treatment of this disease; Ncm: the number of citations of the plant for all diseases and Nt: the total number of citations with:

• Ip = 0 if (Nc/N) - (Ncm/Nt) < 0 for zero performance, 
• Ip = 1 if 0 < (Nc/N) - (Ncm/Nt) ≤ 1/3 for average performance, 
• Ip = 2 if 1/3 < (Nc/N) - (Ncm/Nt) ≤ 2/3 for good performance, 
• Ip = 3 if (Nc/N) - (Ncm/Nt) > 2/3 for very good performance;

- the divergence of indigenous knowledge on the treatments of the groups of diseases, evaluated by the consensus factor of use Informing consensus factor (ICF) that makes possible to evaluate the consensus on the phytoremedies used on the treatment of groups of diseases and to assess the degree of homogeneity of the information given by respondents ^16-17 and calculated by the formula:

ICF = (Ncu – Neu) / (Ncu – 1)     (5)

where Ncu is the number of usage citations reported for each disease category, and Neu the number of species used for the treatment of each disease category. It varies from 0 to 1 ¹⁸:

• the value 0 is the lowest degree and corresponds to different points of view on the part of respondents in the use of plants to treat a category of diseases,
• values below 0.5 are considered low and indicate a low consensus of plant use,
• the value 0.5 is the average degree of the factor and indicates an average consensus for the use of plants,
• values between 0.5 and 1 are relatively strong degrees and show a relatively high agreement in the use of plants to treat a category of diseases,
• the value 1 is the highest degree showing a total consensus in the use of plants to treat a category of diseases.

Chemical screening of aqueous extracts of aromatic plant organs

The phytochemical screening of extracts obtained after aqueous maceration of the aromatic plant organs used in the recipes was carried out qualitatively using standard colouring and precipitation methods ^19-20. Extracts were analysed for determining the composition of main secondary metabolites such as flavonoids (cyanidin test), alkaloids (Dragendorff test), saponins (foaming test), triterpenes and steroids (Liebermann-Buchard test), polyphenols and tannins (ferric chloride test) as well as coumarins in the organs of the most stressed aromatic plants ¹⁹.

Statistical analyses

The survey data was placed in the Excel spreadsheet in the form of citations and codes were assigned to the aromatic plants identified as well as to the groups of diseases treated by the aromatic plants. These data were edited allowing the calculation of frequencies in the number of citations.

RESULTS

Sociodemographic profile of respondents

One hundred and eighty-eight (188) people were interviewed, out of which. 113 informants distributed in three neighborhoods (39 in Bonendalé, 37 in Bonamatoumbé and 37 in Bwadibo) made their contributions on traditional knowledge and uses of medicinal plants. Women were the most represented respondents at 74.35%. Among them, those whose ages varied between 41-60 years represented 32.74%. Women originating from Littoral Region represented 20% and preferentially solicit plants such as: Allium sativum, Annona muricata, Curcuma aromatica, Cymbopogon citratus, Daucus carota, Ocimum basilicum, and Zingiber officinale. Men represented 25% of respondents and those whose age varies between 20-40 years represented 12%. Also, those originating from the Littoral Region represent 9% and solicit plants such as: Ageratum conyzoides, Cymbopogon citratus, and Eremomastax speciosa (Table I). Surveys showed 83 medicinal plant species grouped into 76 genera and distributed in 41 families. The Asteraceae family (6 species) was among the most represented, followed by the Lamiaceae family (4 species) and the Poaceae family (4 species). The species most requested by respondents were Ocimum gratissimum (48 citations), Ageratum conyzoides (31), Cymbopogon citratus (30), Citrus limon (28), Allium sativum (18), Zingiber officinale (15), Annona muricata and Vernonia amygdalina (14 citations each) (Table II).

Table I: Socio-demographic profile of respondents in the Douala IV Sub-Division

Table II: Most cited families in requested medicinal plant species in the Douala IV Sub-Division

Medicinal aromatic plants

Thirty-one species were recognized and identified as aromatic plants by the population of Bonendalé, Bonamatoumbé and Bwadibo, representing 37.34% of the medicinal flora. The species of aromatic plants listed in Table III, belong to 17 families and are distributed in 23 genera. The most represented families were Lamiaceae and Zingiberaceae (4 species each), Rutaceae, Amaryllidaceae and Apiaceae (3 species each), Solanaceae and Annonaceae (2 species each).

Table III: Families of identified aromatic plant species in the Douala IV Sub-Division

Ethno-medicinal characterization of aromatic plants

Traditional healers use aromatic plants in combination to prepare recipes against diseases and related symptoms. Among these plants, some are used both as main plants and/or as associated plants (Allium sativum, Ocimum gratissimum) whereas others are only requested as associated plants (Aframomum exscarpum, Tetrapleura tetraptera). A total of 168 recipes were recorded, including 89 recipes for plants in combination (52.97%) and 79 single-specific recipes (47.02%). Different organs were taken from the vegetative part of aromatic plants to prepare recipes against diseases and symptoms (Figure 2, Table V). These included leaves (114 citations, 50.80%), fruits (49 citations, 21.87%), bulbs (24 citations, 10.71%), rhizomes/roots (20 citations, 8.92%), flowers (11 citations, 4.91%), stems (4 citations, 1.78%) and bark (2 citations, 0.89%). 

The extraction methods for facilitating the administration of the active ingredient of aromatic plants were: the decoction, trituration, maceration, infusion, grinding, calcination, poultice, chewing of the raw organ, drying followed by pulverization of the organ (Figure 2). The infusion (33.33%) was the most used method of preparation, followed by decoction (22.61%), and trituration after heating the organ (17.56%). Six (06) routes of administration were described by the population (Figure 3): oral route (75%), rectal route (7.02%), nasal route (5.88%), cutaneous route (5.93%), steam bath (5%) and ocular route (1.17%). For conservation, traditional medicines are mostly kept at an ambient temperature (53%) not exceeding 25°C, in a cool place (8%). A large part (39%) of the recipes that cannot be kept is thus used immediately after preparation.

Figure 2: Some organs of aromatic plants used by local population of Douala IV. a: Leaves of Petroselium sativum; b:  Leaves of Ocimum basilicum; c:  Fruits of Capsicum frutescens; d:  Fruits of Aframomum melegueta; e:  Seeds of Ricinodendron heudoloti; f:  Fruits of Allium sativum; g:  Leaves of Ocimum gratissimum; h:  Seeds of Piper nigrum; i: Leaves of Cymbopogon citratus; j:  Rhizomes of Zingiber officinale; k:  Fruits of Citrus limon; l: Floral buds of Syzygium aromaticum

Figure 3: Different mode of (a) preparation and (b) administration of medicinal recipes in the Douala IV Sub-Division

Diseases cured by aromatic plants

The recipes prepared by the local population of Douala IV sub-division from aromatic plants were associated with the treatment of 51 diseases and related health problems (Table V and VI). Among these diseases, the most treated were: malaria (22 citations), cough (21 citations), typhoid (12 citations), colds (9 citations), diaper rash (8 citations), flu (6 citations), hypertension blood pressure (4 citations), nerve ache (4 citations), diabetes (3 citations), fontanel (3 citations), stomach ache (3 citations), spleen inflammation (2 citations), female worms (2 citations) and colic (2 citations). All these diseases have been grouped into 11 major groups, the most important of which are diseases of the respiratory system (38 citations) and infectious and parasitic diseases (35 citations).

Ethnobotanical indices 

Aromatic plants with a high use value were determined. The use values vary between 0.22 (Citrus limon) and 1.5 (Apium graveolens). The calculation of the contribution of the plant in the constitution of the receipts (Cpr) showed that Ocimum gratissimum (28.57%), Cymbopogon citratus (17.85%), Citrus limon (16.66%) and Allium sativum (10.71%) were the aromatic plant species most involved in the preparation of recipes (Table VI). The analysis of the performance indices (Ip) by disease cited highlights three categories of species: good performance (Ip = 3), average performance (Ip = 2) and non-performing (0 ≤ Ip ≤ 1). Zingiber officinale (Ip = 3) was the most effective species in remedying cough problems. Citrus limon (Ip = 3) was the most efficient species for the treatment of typhoid fever. Cymbopogon citratus (Ip = 3) has a good performance for the treatment of malaria. Some species mentioned have multiple uses both in the same group of diseases and for diseases of different groups. Cymbopogon citratus and Citrus limon display respectively an average performance for typhoid and malaria which are diseases of the same category (Table IV). Ocimum gratissimum showed a good performance against colds and an average performance against cough (diseases of the same group) and also showed a good performance for diaper rash and stomach ache. In order to assess the informant agreements on the therapies reported for each pathological group treated by the listed aromatic plants, the degree of consensus of use (ICF) of the plants was calculated. This degree of consensus revealed 5 categories of diseases: respiratory system (0.75), infectious and parasitic (0.73), skin and cellular tissue (0.72), digestive system (0.64), nervous system and sense organs (0.6) (Table V).

Table IV: Aromatic plants showing performance against some diseases in the Douala IV Sub-Division

Table V: ICF of the diseases treated by the aromatic plants in the Douala IV sub-division

Table VI: Characterization of recipes and calculation of ethnobotanical indices in the Douala IV Sub-Division 

Therapeutic properties of bioactive metabolites of aromatic plants

The metabolites that might be responsible for the therapeutic properties of the selected aromatic plants were determined using standard methods of staining and precipitation. The results indicated the presence of alkaloids in all the organs of aromatic plants having undergone the Dragendorff test except the flower buds of Syzygium aromaticum. Phenolic compounds of the phenol class are also present in the organs of aromatic plants. Many classes of phenolic compounds were found in the organs of each of the aromatic plants including flavonoids, polyphenols, tannins and coumarins. Furthermore, terpenes, sterols and saponins were also present in the aqueous extracts of the organs of aromatic plants (Table VII).

Table VII: Bioactive metabolites of aromatic plants in the Douala IV Sub-Division

DISCUSSION

The popular knowledge admitted the use of medicinal plants to fight against several diseases ^{1-3-4-8-10-12-17}. The African population resumed some of them and aromatic plants notably as an alternative fight against this pandemic and many other diseases ^5-6-9-40. In the following lines, we discuss results from the ethnobotanical study of aromatic plants in the Douala IV subdivision, the associated receipts and indices as their pharmacological properties of bioactive metabolites used during the pandemic and possibly used for other diseases.

Ethnobotanical aromatic plants from the Douala IV sub-division

Aromatic plants are dominantly used in culinary arts and seem to be a prerogative of women and their strong involvement (75%) in this study. It shows the highest representation of adults with greatest experience in the practice of pharmacopoeia compared to young people who have less confidence in herbal medication and more often resort to modern medication ^21-22.The great number of information on 83 plant species that included 31 species of aromatic plants used in the preparation of 168 recipes revealed different plant organs for medicinal preparations and different methods for extraction and administration of the active ingredient. This highlights the heterogeneous nature of ethnobotany ^22-23-24. The thirty-one (31) aromatic species identified defined 23 genera belonging to 17 families dominated by the Lamiaceae and Zingiberaceae (04 species each); Apiaceae, Rutaceae and Amaryllidaceae (03 species each). Mpondo Mpondo et al. ²⁵ in a study carried out in the eastern part of Douala on coumarin plants already found that Apiaceae and Lamiaceae were part of the most represented families with Fabaceae and Asteraceae. Spices and condiments used to make traditional dishes with enormous therapeutic potential are mainly distributed in the Apiaceae, Lamiaceae, Amaryllidaceae and Zingiberaceae families in agreement with previous results ^{10-26-27-28-29-30}.

Aromatic plant recipes

Florula of the listed aromatic plants is essentially made up of herbaceous plants (63.3%). The use of herbaceous plants could be explained by the premonitory function of aromatic plants, which are spices and condiments defined by their perennial character ²⁰. The use of leaves has importance linked to the morphological type that predominates in the florula of aromatic plants inventoried and also as the main composition of herbaceous plants. They are used in the culinary arts as spices or as flavourings, in herbal medicine for their active ingredients or essential oils extracted from organs as leaves and fruits of aromatic plants ^8-25-26. In the light of the results, it appears that the infusion of the leaves (33.33%) is the most widespread mode of preparation. In woody plants, the bioactive metabolites after synthesis in the leaves are stored in the fruits and barks, in herbaceous plants, large quantities of bioactive metabolites remain concentrated in the synthesis places which are mostly the leaves ^31-32. These results corroborate with those found by Fathia et al. ²² who reported infusion as the most used method for relatively soft organs. Decoction and infusion, in addition to facilitating the extraction of the active ingredient, would make it possible to increase the body's temperature, thus weakening the wall of certain bacteria and thus facilitating the pharmacodynamics of the active ingredient ^33-34.

Ethnobotanical indices of aromatic plants

Regarding the contribution of aromatic plants for the preparation of medicinal recipes, plants such as Ocimum gratissimum, Cymbopogon citratus, Citrus limon, Allium sativum, Zingiber officinale, Annona muricate and Syzygium aromaticum stand out as the aromatic plants most involved in medicinal preparations. The strong implication of these species suggests an additional contribution of these to obtain the expected therapeutic effect. Holders of ancestral knowledge make empirical associations of plants in the same recipe with the aim of seeking either a synergistic effect of the active ingredients, or an attenuating effect for the active ingredients deemed to be aggressive, irritating or even toxic for the body ²³. Therapeutic use values of the exploited species showed that plants do not benefit to the same credit or importance for the population surveyed. Some plants like Citrus limon (VUT=0.22), Ocimum gratissimum (VUT=0.23) and Cymbopogon citratus (VUT=0.23), although requested by several respondents, are used for the treatment of many diseases. They will therefore have a low use value ^17-23. Apium graveolens (VUT=1.5) cited by 3 informants for 3 different diseases is found to have the highest use value. Dassu et al. ¹⁵ showed that the importance given to a species does not depend exclusively on its availability but also on its ability to meet the needs of population in the different categories of uses when it is mentioned for several therapeutic uses by few informants. Some aromatic plants such Allium sativum, Cymbopogon citratus, Ocimum gratissimum showed a good performance for a given disease and an average performance for another disease. This could be justified by the fact that these plants are cited several times by various users to treat the same disease or find in the treatment of many other associated diseases or symptoms ^9-32. This is consistent with the relatively high agreement of the ICFs obtained on aromatic plants treating diseases of the respiratory system, infectious and parasitic diseases, skin diseases and cellular tissue, diseases of the digestive system as well as diseases of the circulatory system. High ICFs values for certain categories of diseases showed that the probability that a person living in the surveyed area is subject to one of the diseases of this group is high and provide sufficient information on the diseases affecting the studied population ^17-35. This index supports the fact that some species are unanimous among respondents used in medicinal recipes. This strong demand could lead to more pressure on the flora of aromatic plants, which therefore deserves conservation. The Ip and ICF also grouped aromatic plants according to their pharmacological effect, symptomatologies and treating plants treating similar diseases. Holders of ancestral knowledge do not have perfect control of the symptoms of the diseases for which they prescribe the treatments, equating the symptoms of malaria with those of typhoid and jaundice and justifying misadministration of medicinal plants. These diseases present similar health problems such as digestive disorders (dysentery) and fever are among the symptoms identified as associated with Covid-19. According to Sartoratto et al. ³⁶, plant extracts, such as spices and aromatic herbs have antimicrobial properties because they are rich in phenolic secondary metabolites which are natural antioxidants and antimicrobials. Extracts of spices and aromatic herbs also have an inhibiting effect on the growth of several bacteria and fungi responsible for foodborne illnesses ^36-37.

Pharmacological properties of bioactive metabolites of aromatic plants

The studied aromatic plants have even secondary metabolites that vary from one organ to another for the same plant in agreement with previous findings after e.g.: ^24-31-32-38. The abundance of these metabolites depends on the extraction solvent ²⁴. The seed extracts of Ricinodendron heudolotii reveal different secondary metabolites depending on whether the extraction solvents are Hexane, Ethyl acetate, Ethanol, Methanol and water ³⁹. The infusion of the mixture of aromatic plants consisting of garlic (Allium sativum), ginger (Zingiber officinale), onion (Allium cepa) and clove (Syzygium aromaticum) to which Lemon (Citrus limon) is added to it, was very popular and widely consumed by the population of Bonendalé, Bonamatoumbé and Bwadibo during the pandemic period. This mixture has been recognized with lemongrass leaf tea (Cymbopogon citratus) as having played a major role in strengthening the resilience capacities of consumers with Covid-19 disease. These results corroborate those of Kuete-Sezin et al. ⁶ who showed that out of 872 patients cured by medicinal plants during the pandemic, 244 were cured with “grandmother’s potion”, 224 with lemongrass leaf tea and 88 with neem leaf tea (Azadirachta indica). Fongnzossie Fedoung et al. ⁴⁰ have shown that molecules such as Allicin from Allium sativum, Gingerol from Zingiber officinale, Hesperidin, Naringenin and Quercetin from Citrus limon are secondary metabolites whose beneficial effects against Covid-19 disease are significant. These molecules give to the plants antiviral, antibacterial, antiparasitic, antidiarrheal, anti-inflammatory, antioxidant and analgesic properties, thus helping to treat respiratory diseases, infectious and parasitic diseases to which the population of Douala IV are subjected to ^41-42-43.

In medicine, alkaloids are used as major analgesics (morphine), antimalarial (quinine), to combat excess uric acid (colchicine) ^38-44. Alkaloids from the leaves of Cymbopogon citratus would play an antipyretic role to lower the fever induced by diseases such as typhoid and malaria. They have been recognized as having pronounced properties against parasites of the genera Plasmodium and Entamoeba. Yingyang et al. ⁴⁴ already noted the importance of alkaloids from the Quinolin family (Quinine, Quinonine, Quinidine) and many indole alkaloids in the treatment of malaria and diarrhoea.  Coumarin plants and more specifically those of the Apiaceae family have the ability to promote the expulsion of intestinal gas leading to a reduction in bloating and flatulence. They would stimulate the secretion of the digestive glands leading to a good degradation of food and limit undesirable fermentations. They increase stomach acid production contributing to good disinfection of the food bolus ²⁸. Ocimum gratissimum and Ocimum basilicum are said to have significant antispasmodic activity and marked antimicrobial properties ^25-38. Tannins are endowed with remarkable antibacterial and antifungal activities. Their importance in traditional medicine has been reported in the treatment of infantile diarrhea, bronchitis, and cough as well as in the treatment of venereal diseases ^30-31. This could explain the fact that Syzygium aromaticum and Zingiber officinale have very good performances in the treatment of some of these diseases. In addition, the ability of tannins to prevent and repair damage caused by Reactive Oxygen Species (ROS) gives them significant importance in activating the immune defense and the ability to reduce the risk of cancer and other degenerative diseases ^29-30. The flavonoids of Annona muricata and Allium sativum as powerful antioxidants allow the direct trapping of ROS, the inhibition of enzymes and chelation of the metallic traces responsible for the production of these ROS ³². Vitamin C is a flavanic compound present in the fruits of Citrus limon ³⁸. According to Agbor Agbor and Ndjib; Dibong et al.; Mpondo et al.; Vandi et al. and Fongnzossie Fedoung et al. ^{9-23-29-30-40} lemon juice when added to certain preparations to treat malaria, influenza, typhoid, diarrhea and Covid-19; would contribute to bring tone to the patient and to reinforce his immune defence.

CONCLUSION

We evaluated the knowledge on the Cameroonian medicinal flora, mainly on the species of aromatic plants in the purpose to determine the ethnobotanical knowledge and index as different bioactive compounds of aromatic plants used for health diseases during the pandemic due to Covid-19 in the Douala IV sub-division (Littoral region, Cameroon). From the semi-structured survey and the calorimetrically these aromatics, it appears at the end that the population used endogenous medicinal plants including aromatic ones for treating several diseases including the targeted Covid-19 and associated reparatory problems. Among the aromatic plants, the Lamiaceae and Zingiberaceae with the Ocimum gratissimum and Zingiber officinale were the most cited in the composition of recipes. Leaves (50.80%) were the most used organs to prepare the infusions (33.33%) and the decoctions (22.61%) that was administered by the oral route. These plants are recognised as capable in the treatment of many diseases including malaria, cough and typhoid with an ICF (0.75) against respiratory diseases and good performance (Ip = 3). Alkaloids and phenolic rich extracts of aromatic plant organs showed their ability to treat respiratory and other infectious diseases. They could be used as an alternative to fight against Covid-19 and represent serious candidates for the production of Improved MTA.  

ACKNOWLEDGEMENT

The authors are grateful to the Government of Cameroon through its Ministry of Higher Education for providing Research Modernization Allowance that partially supports field trips. Authors would also like to thank the contributions received from the members of the Laboratory of Plant Biology, and the anonymous reviewers for their constructive suggestions.

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