Three new biphenyl constituents from Colocasia antiquorum var. esculenta

Colocasia antiquorum var. esculenta (Araceae) is native to tropical Asia and Polynesia. C. antiquorum var. esculenta is a staple food in many tropical and subtropical areas of the world, and is a natural inhibitor of polyphenol oxidase [1]. To the best of our knowledge, the active phytochemical principles of this source are unknown. Therefore, as part of our continuing search for potential lead compounds for drug development from Korean medicinal plant sources, we performed a phytochemical investigation of this herb. Dried tuber-barks of C. antiquorum var. esculenta (3.8kg) were extracted with 85% MeOH using an ultrasonic apparatus for 1h. The extract (350g) was dissolved in water and partitioned with EtOAc to give an EtOAc extract (36g). Purification of the EtOAc soluble fraction by column chromatography led to the isolation of three new biphenyl derivatives, 2,2'-dihydroxy-4-(3-hydroxy-1-propenyl)-4'-(1,2,3-trihydroxypropyl)-biphenyl (1), 2,2'-dihydroxy-4-(3-hydroxy-1-propenyl)-5'-(1,2,3-trihydroxypropyl)-biphenyl (2), and 2,2'-dimethoxy-4-(1,2,3-trihydroxypropyl)-4'-(1,2,3-trihydroxypropyl)-biphenyl (3), together with a known compound, 2-hydroxy-3,2'-dimethoxy-4'-(2,3-epoxy-1-hydroxypropyl)-5-(3-hydroxy-1-propenyl)biphenyl (4) [2]. The identification and structural elucidation of these compounds were based on 1D- and 2D-NMR spectral data.

References: 1. Lee, M. Y. et al. (2007) Food Chem. 105:528.

2. Morita, H. et al. (1992) Phytochemistry 31:3993.