Assessing medicinal plants traditionally used in the Chirang Reserve Forest, Northeast India for antimicrobial...

Knowledge on the use of plants for different ailments by the tribals of the Chirang Reserve Forest (CRF, Northeast India) was used to assess the potential of these plants for treating viral, bacterial and fungal infections.

Fieldwork in the CRF documented the use of plants for the treatment of various human ailments. The ethnobotanical data were analysed using different quantitative indices viz. Informant Consensus Factor (ICF), Relative Frequency Citation (RFC), Fidelity Level (FL), Relative Popularity Level (RPL) and Rank Order Priority (ROP). For each plant, four extracts were prepared with different solvents (water, ethanol, acetone and hexane) and tested for bioactivity such as antiviral (Enterovirus 71) and antimicrobial (E. coli, S. aureus, C. albicans) effects. To develop fingerprints, thin layer chromatography (TLC) was carried out with at least one extract of each active plant.

Thirty-seven plant species belonging to 26 families used frequently in the CRF were categorised into twenty disease(s) and markedly high ICF values (0.5-1) were found. The FL of the 19 most important plant species ranged from 10% to 100%. Aglaia spectabilis, Actinodaphne obovata, Bischofia javanica, Gmelina arborea, Hodgsonia macrocarpa and Mesua ferrea were the most popular plant species with RPL values > 0.4. The most commonly treated diseases were skin infections, worm infections, diarrhoea, dysentery, common cold and throat infections, cough and respiratory problems, fever, malaria, rheumatism, pain, stomach ache and gastric problems. Among the taxonomic families, the most represented are Lauraceae (4 species); Meliaceae (3 species), Euphorbiaceae, Elaecarpoceae, Magnoliaceae, Malvaceae, Moraceae and Myrtaceae (2 species each). Of these, 35 plants (95%) with 91 of their extracts were found to be active against S. aureus (inhibition > 50%). Similarly, over half of the tested plants inhibited growth of E. coli (19 plants with 31 extracts) while 9 plants with 14 extracts were active against C. albicans. Moreover, one-third (12) of the plants showed anti-enteroviral activity. TLC analysis of the extracts indicates the presence of different phytochemical classes such as alkaloids, flavonoids, glycosides, terpenoids and saponins based on observing characteristic spots under visible or UV light (254 or 360 nm), with or without derivatisation.

Thirty-seven plants commonly used by the tribes of the CRF as anti-infective agents offer perspectives for further research, as the phytochemistry and phytopharmacology for most of these plants have not been published to date.