Relationships between degree of polymerization and activities: A study on condensed tannins from the bark of Ficus altissima

Condensed tannins were isolated from the bark of Ficus altissima and fractionated into four subcomponents on a Sephadex LH-20 column with 60 %, 80 %, 100 % methanol, and 70 % acetone, separately. Their structures were characterized by MALDI-TOF MS coupled with HPLC-ESI-MS and confirmed to be polymers of B-type procyanidin glucosides, procyanidins, and prodelphinidin glucosides. The degree of polymerization (DP) of these polymers was as high as 21, and the mDPs of the four subcomponents were calculated as 2.4, 6.6, 10.5 and 13.4, respectively. They competitively or noncompetitively suppressed the activities of tyrosinase and α-glucosidase through hydrogen bonding and hydrophobic interaction. And they also showed a powerful antioxidative activity. Correlation analyses verified that the anti-tyrosinase capacity exhibited a significant positive correlation (R2monophenolase = 0.9167 and R2diphenolase = 0.9302) with mDP within the methanol-water system, and the anti-α-glucosidase activity also showed a significant positive correlation with the mDP (R2 = 0.9187). In contrast, the antioxidant capability showed a significant negative correlation with the mDP (R2DPPH = 0.9258, R2ABTS = 0.9372). This study confirmed that condensed tannins from the bark of F. altissima were desirable anti-tyrosinase, anti-α-glucosidase, and antioxidant agents, and elucidated the relationships of their mDP (molecular weight) and activities, which provided a scientific basis for the comprehensive utilization of these polymers in the food, cosmetics, medicine and other fields.