ANTIALLERGIC AND ANTIDIABETIC COMPOUNDS FROM SOME PHILIPPINE MEDICINAL PLANTS
In collaboration with Philippine scientists, we have been studied on biologically active constituents from Philippine Medicinal plants.
Antiallergic Activity
Histamine released from mast cells caused dermatitis in type-I allergic reaction. In search for possible anti-allergic substance, using in vitro mast cell assay system, we found effective plants, such as Lagundi, Sambong and Tsaang Gubat. From the effective fraction of Tsaang Gubat (Photo) = Ehretia microphylla (Boraginaceae), rosmarinic acid (1), unique dimeric prenyl-naphthoquinones, microphyllone (2) and it's congeners (3-6) were isolated and characterized with spectral data, and their structure-activity relationship is discussed.
From the other plant of the same genus, E. philippinensis, unusual noncyanogenic cyanoglucosides, simmondsin (7), and its congeners, ehretiosides A1-3 (8-10) and B (11) were isolated with 1. Simmondsin is a constituent of Jojoba, and known to have inhibitory activity of feeding, suggestive for application to diet food.
Anti-diabetic Activity
Activation of the glucose transporter activity would cause several physiological effects, such as lowering blood glucose level. No other agent able to increase glucose transporter activity is known except insulin, which regulates blood sugar level intrinsically. Screening of plant extracts by measuring glucose transport activity led to find some effective plants, such as Abutra, Akapulko, Makabuhai and Banaba. One of the active principles from Banaba = Lagerstroemia speciosa (Lythraceae) was a triterpene, corosoric acid. Further isolation and characterization of effective compounds in this plant are in progress.