An Overview on Decalepis: A Genus of Woody Medicinal Climbers

Decalepis is one of the most important endangered woody medicinal climbing members of “Periploaceace” family. It comprises five species of twining vines and erect shrubs, D. hamiltonii, D. arayalpathra, D. salicifolia, D. khasiana and D. nervosa. Four of the five species of Decalepis are endemic to the Eastern and Western Ghats of peninsular India; the exception, D. khasiana, is geographically isolated from the peninsular species, occupying forest areas in the Meghalaya state in the easternmost part of India, Bangladesh, Laos, Myanmar and parts of Southern China. D. hamiltonii is the type species and most widespread of the Indian endemics. Three species (D. arayalpathra, D. hamiltonii and D. salicifolia) have clusters of numerous fleshy and tuberous roots with a sweet, vanilla-like fragrance due to the presence of 2-hydroxy-4-methoxy benzaldehyde (2H4MB). The tuberous roots of D. arayalpathra and D. salicifolia are moniliform, while those of D. hamiltonii are cylindrical. The roots of D. khasiana are documented as being non-tuberous, and fragrant due to an isomer of vanillin. Four of the five species of Decalepis (all except D. nervosa) are utilized in tribal and traditional Indian and Chinese medicine for the treatment of a wide range of ailments including those of the digestive system, lungs and circulatory system. Presently the three peninsular Indian species of Decalepis are threatened in the wild, and listed as endangered (D. hamiltonii) to critically endangered (D. arayalpathra and D. salicifolia) due to over-exploitation and habitat loss. During last few years considerable efforts have been tried to conserve this valuable endangered liana using different strategies of plant tissue culture viz., in vitro shoot regeneration (direct or indirect) and root induction, somatic embryogenesis, hydrogel encapsulation, normal root culture and hairy root culture. The present review provides up-to-date baseline information of all the species of this valuable endangered and endemic medicinal genus for further research work.