Isolation of (2S)-naringin from very immature pomelo peels cultivated at Chau Thanh district, Tien Giang province

With an annual pomelo production of 800,000 tons, the isolation of naringin from the pomelo peel is an interest attracting research. Besides ripe ponelo peel, very immature pomelo discarded during the cultivation can also be considered as a potential source of raw materials for the isolation of naringin from peels because naringin exhibits diverse biological activities. The results of RP-HPLC-UV analysis on naringin, isolated from the peel of pomelo, showed that the naringin content in the pomelo peel, the isolation yield, and the chemical purity decreased with the maturity of pomelo. Particularly, the study found that the chemical purity (% naringin) of very immature pomelo peels (from 7-15 days old) possessed naringin products containing up to 92.3%, while % naringin products isolated from ripe pomelo peels (greater than 90 days old) contained only 53.3%. Furthermore, the chiral-HPLC-UV analysis showed that the racemization at C-2 of the isolated naringin increased promptly (the (2S)-naringin was converted to the (2R)-naringin) following the maturity. The enantiomeric excess (% ee) of (2S)-naringin in the very immature peels (pomelo of 7‒15 days old) possessed 79.3% while the ripe peels (pomelo over 120 days old) was -2.2%. Therefore, the very immature peel of pomelo would be a potential source of raw materials for the isolation of a high purity naringin. This could contribute the economic value to Vietnam's pomelo farming.