Structural characterization and bioactivity of proanthocyanidins from indigenous cinnamon (Cinnamomum osmophloeum)

Barks and twigs of common species of cinnamon with abundant proanthocyanidins are used as a spice, fold medicine or supplement. Cinnamomum osmophloeum is an endemic species in Taiwan and coumarin was not detected in the oil of the C. osmophloeum twig. The present study aimed to evaluate the relationship between the bioactivities and proanthocyanidins of C. osmophloeum twig extracts (CoTE). The n-butanol soluble fraction from CoTE was divided into 10 subfractions (F1-F10) by Sephadex LH-20 gel chromatography. The antihyperglycemic activities were examined by α-glucosidase, α-amylase and protein tyrosine phosphatase 1B inhibitory assays. Total antioxidant activities were examined by 2,2-diphenyl-1-picrylhydrazyl free radical scavenging and ferrous ion-chelating assays.

The results revealed that subfractions F6-F10, with high proanthocyanidin contents, showed excellent antihyperglycemic and antioxidant activities. Subfractions F6-F10 were analyzed further by matrix-assisted laser desorption/ionization-time of flight/mass spectrometry and thiolysis-reversed-phase high-performance liquid chromatography/tandem mass spectrometry methods. The results showed that the mean degrees of polymerization of proanthocyanidins in subfractions F6-F10 ranged from 3.5 to 5.1, with the highest degrees of polymerization of proanthocyanidins reaching 8 in subfractions F8-F10. Two compounds in F6 were identified as cinnamtannin B1 and parameritannin A1. These proanthocyanidins contained at least one A-type and major B-type linkages.

These results demonstrate that proanthocyanidins are associated with their antihyperglycemic and antioxidant activities in CoTE. © 2016 Society of Chemical Industry.