Among the different metabolites found in the Passiflora species, flavonoids have been related to some of the therapeutic effects of these plants. In the case of Passiflora ligularis, the presence of these metabolites has been related to a promising hypoglycemic effect. This study aimed to optimize the total flavonoid content (TFC) of P. ligularis leaf extract in order to improve its therapeutic activity. The effect of three variables (ethanol percentage, temperature and time) on the ultrasound-assisted flavonoid extraction was evaluated by means of response surface methodology. The effect of increasing the flavonoid content on the extract activity was evaluated with an in vitro antiglycation assay and an in vivo glucose tolerance test in mice. The optimal extraction conditions were 63% ethanol, 70ºC, and 33 minutes. The predicted maximum flavonoid yield (57.77 mg-equivalent isoquercetin/g dry extract) correlated with the experimental value (59.76 ± 1.90 mg-eq isoquercetin/g dry extract) and the extraction process proved to be highly reproducible, suggesting that ultrasound assisted extraction is a simple, inexpensive and effective alternative technique for the extraction of flavonoids in Passiflora species. Moreover, the optimized extract exhibited the highest antiglycation activity against all the experimental design treatments and showed an enhanced hypoglycemic effect in mice compared to a traditionally extracted beverage.
Key words: Passiflora ligularis, ultrasound-assisted extraction, flavonoids, optimization, hypoglycemia.