Indole and flavanoid constituents of Wrightia tinctoria, W-tomentosa and W-coccinea

Members of the genus Wrightia, viz. W. tinctoria, W. tomentosa and W, cocci nea, have been investigated for their chemical constituents with a view to locating their bioactive principles. Indigotin 3, indirubin 6, tryptanthrin 8, isatin 5, anthranillate 7 and rutin 9 have been isolated and identified as major constituents of W. tinctoria and W. tomentosa. Anthranillate 7 an d rutin 9 are the major constituents of W. coccinea. The identities of thes e compounds have been established by comprehensive chromatographic (HPTLC, HPLC) and spectroscopic (UV-VIS, IR, EI-MS) techniques, using markers and b y synthesis, where possible. While indigotin is found to be native in the l iving plants (in fresh leaves), indirubin was found to be an artifact forme d only during drying process after harvesting of the leaves. This transform ation is presumably caused by the intact hydrolytic enzyme system(s) and by autoxidation. Seasonal variation studies of the chemical constituents of l eaves, using HPTLC and HPLC analyses, revealed similar variation patterns i n the three species. The concentration of indigotin-indirubin combination s teadily increases from August to November. In contrast, concentration of is atin and anthranillate increases in the months of December and January, at the expense of indigotin-indirubin. isatin is produced by the autoxidation of indigotin. Tryptanthrin concentration also increases, periodically, in M ay (at the expense of isatin) and in January. Plausible pathways for the fo rmation of these indole metabolites are appraised on the basis of circumsta ntial and synthetic evidence.