Anti-Obesity Evaluation of Averrhoa carambola L. Leaves and Assessment of Its Polyphenols as Potential α-Glucosidase Inhibitors.

Averrhoa carambola L. is reported for its anti-obese and anti-diabetic activities. The present study aimed to investigate its aqueous methanol leaf extract (CLL) in vivo anti-obese activity along with the isolation and identification of bioactive compounds and their in vitro α-glucosidase inhibition assessment. CLL improved all obesity complications and exhibited significant activity in an obese rat model. Fourteen compounds, including four flavone glycosides ( 1 - 4 ) and ten dihydrochalcone glycosides ( 5 - 12 ), were isolated and identified using spectroscopic techniques. New compounds identified in planta included ( 1 ) apigenin 6- C -(2-deoxy- β -D-galactopyranoside)-7- O - β -D-quinovopyranoside, ( 8 ) phloretin 3'- C -(2- O -( E )-cinnamoyl-3- O - β -D-fucopyranosyl-4- O -acetyl)- β -D-fucopyranosyl-6'- O - β -D fucopyranosyl-(1/2)-α-L arabinofuranoside, ( 11a ) phloretin3'- C -(2- O -( E )-p-coumaroyl-3- O - β- D-fucosyl-4- O -acetyl)- β -D-fucosyl-6'- O -(2- O - β -D-fucosyl)-α-L-arabinofuranoside, ( 11b ) phloretin3'- C -(2-O- (Z) -p -coumaroyl-3- O - β -D-fucosyl-4- O -acetyl)- β -D-fucosyl-6'- O -(2- O - β -D-fucosyl)-α-L-arabinofuranoside. Carambolaside M ( 5 ), carambolaside Ia ( 6 ), carambolaside J ( 7 ), carambolaside I ( 9 ), carambolaside P ( 10a ), carambolaside O ( 10b ), and carambolaside Q ( 12 ), which are reported for the first time from A. carambola L. leaves, whereas luteolin 6- C -α-L-rhamnopyranosyl-(1-2)- β -D-fucopyranoside ( 2 ), apigenin 6- C - β -D-galactopyranoside ( 3 ), and apigenin 6- C - α -L-rhamnopyranosyl-(1-2)- β -L-fucopyranoside ( 4 ) are isolated for the first time from Family. Oxalidaceae. In vitro α-glucosidase inhibitory activity revealed the potential efficacy of flavone glycosides, viz., 1 , 2 , 3 , and 4 as antidiabetic agents. In contrast, dihydrochalcone glycosides ( 5 - 11 ) showed weak activity, except for compound 12 , which showed relatively strong activity.