Researches On Chemical Consitituents And Hypoglycemic Activity Of Litchi (Litchi Chinensis Sonn.) Seeds

Litchi (Litchi chinensis Sonn.) seeds were used as a traditional Chinese medicinal for hundred years in China, and it was reported that litchi seeds possess anti-diabetic effects, antihyperlipidaemic, antiplatelet, anti-tumour and antiviral activities, however the active compound to offord the hypoglycemic activity was not found in litchi seeds. Using a bioactivity-guided method, a research was taken to study the chemical constituents possessed theα-glucosidase inhibitory activity from Litchi seeds and try to explain the bioactivity foundation.1. 95% ethanol extract of litchi seeds was text on the hypoglycemic assay on anminal. The diabeteic rats as model, metformin as a positive control, the results showed that the low dose group of the 95% ethanol extract could lower blood glucose level of rats compared with the model group, the hige dose group of the extract showed stronger activity, almost to the value of the positive control group.2. The screening model ofα-glucosidase inhibitory assay was established, 50% ethanol extract of litchi seeds showed stronger inhibition toα-glucosidase than the control, acarbose. The result was consistent with that of animal experiment.3. 26 compounds were isolated from the active fraction of 50% ethanol extract of litchi seeds by a bioactivity-guided method. Using morden chromatographic methods (IR, HRESI-MS, 1H-NMR, 13C-NMR, HMQC, HMBC), 20 compounds were identified, including two new flavanone compounds, one new natural compound, and 12 compounds were reported in Litchi for the first time. Two new compounds were pinocembrin-7-O-[(2'', 6''-di-O-α-L- rhamnopyranosyl)-β-D-glucopyranoside] (A7), and pinocembrin-7-O-(6''-O-α-L-arabinose-β-D-glucopyranoside) (A19), a new natural product was (2R)-naringenin-7-O-(3''-O-α-L- rhamnopyranosyl-β-D-glucopyranoside) (A8).4. The isolated compounds were tested on the inhibition toα-glucosidase, A12 and A13 had siginificant inhibitory activity in the assay at 1mg/mL, showed stronger inhibition than acarbose.5. The method of PMP derivatisation was performed to investigate the component sugar of the compounds. 6. The component of volatile material was studied by GC-MS method. 53 components were identified, accounting for 60.536% peak area of total outflow.16 flavanoids compounds were isolated from theα-glucosidase inhibitory active fraction of Litchi seeds, and the research also showed some connection between the inhibition onα-glucosidase and structures of constituents. We speculated that flavanoids may be one of the anti-diabetic active components of Litchi seeds.