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 photo- activated 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.