September 2017
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Monochoria vaginalis (Burm.f.) C. Presl ex Kunth (Pontederiaceae) is an aquatic plant native to Asia and pacific islands. The plant is a common weed in rice fields in Sri Lanka. It has numerous medicinal properties, which can be used to treat many communicable and non-communicable diseases. M. vaginalis has been documented for its medicinal value in Sri Lanka as well as in the Asian region where it is considered as a functional food. It is also used for phytoremediation to remove toxic heavy metal contaminants from the environment. A recent study in Sri Lanka reported that consumption of porridge of M. vaginalis, as a remedy for diabetes caused liver damage and the reason was attributed to the presence of phonetically different groups with M. vaginalis, particularly a group with sub-epidermal glands filled with a red colour liquid. Our previous studies on crude extracts of M. vaginalis showed antioxidant and -amylase inhibitory activities. However, the phenetic group with the glands showed cytotoxic and hemolysis activities. The present study reports further phytochemical study on this group of M. vaginalis with sub-epidermal glands. Leaves of M. vaginalis with sub-epidermal glands were collected in August, 2015 and dried leaves were subjected to sequential extraction with hexane, ethyl acetate (EtOAc) and methanol (MeOH). Thin layer chromatographic (TLC) analysis showed the presence of common UV active (254 nm) compounds in hexane and EtOAc extracts. Hence, both extracts were combined and chromatographed over silica gel and Sephadex LH-20, and finally separated by preparative-TLC. The purification furnished four compounds belonging to diarylheptanoids and phenylphenalenones, which were identified as alnustone {(4E,6E)-1,7-diphenylhepta-4,6-dien-3-one} (1), 4-hydroxyanigorufone {2,4-dihydroxy-9-phenylphenalen-1-one} (2), anigorufone {2-hydroxy-9-phenylphenalen-1-one} (3) and anigorootin {rel-(7aR,7bR,14aR,14bR)-7b,14b-dihydro-7a,14a-dihydroxy-6,13-diphenyl-(7H,14H)-diphenalen[2,3,3a,4-b,c,d:2,3,3a,4-g,h,i]pyrano[4,3-c]pyran-7,14-dione} (4). Phenylphenalenones are suggested to be phytoalexins produced in several families of plants, including banana.