Photo-activated DNA binding and antimicrobial activities of alkaloids from Glycosmis pentaphylla

In our screening for photosensitizers from natural resources, four alkaloids were isolated from Glycosmis pentaphylla by various chromatography techniques. Their structures were identified as glycoborinine (1), glybomine B (2), carbalexin A (3) and N-p-coumaroyltyramine (4) by spectral analysis. Their photoactivated antimicrobial activities were evaluated by thin-layer chromatography (TLC) agar overlay assay against Staphylococcus aureus and Bacillus subtilis. It was found that compounds 1 and 4 showed photo-activated antimicrobial activities. Meantime, photo-activated DNA binding activities of these compounds were also assessed by using a specially prepared 1.8 kb DNA fragment and restriction enzymes. Under UVA irradiation, compound 1 showed moderate inhibition on Nde I, Xba I, Nco I and Bcl I which have either 5'-TpA or 5'-ApT and trace or no inhibition on other restriction enzymes. It showed a similar inhibition pattern with the reference 8-methoxypsoralen. However, compounds 2-4 showed no inhibition against any of the restriction enzymes.