Structural Elucidation and Antioxidant Activities of Proanthocyanidins from Chinese Bayberry (Myrica rubra Sieb. et Zucc.) Leaves

Abstract

Proanthocyanidins in Chinese bayberry leaves (PCBLs) were qualitatively analyzed. NMR data suggest that PCBLs are mostly composed of (epi)gallocatechin gallate units. Matrix-assisted laser desorption time-of-flight MS data indicate 95 possible prodelphinidin structures, ranging from dimers to tridecamers. Preparative normal-phase HPLC and further analysis by reverse-phase HPLC together with electrospray ionization MS enabled detection of 20 compounds, including seven newly identified compounds in Chinese bayberry leaves. The antioxidant capacity of PCBLs was evaluated by (1,1-diphenyl-2-picryl-hydrazyl), ferric-reducing antioxidant power, and oxygen radical absorption capacity assays. The EC50 of DPPH radical scavenging activities (as 50% decrease in the initial DPPH concentration) were 7.60 µg. The FRAP and ORAC values were 8859.33±978.39 and 12991.61±1553.34 µmol Trolox equivalents per gram, respectively. The results indicate the high antioxidant potency of PCBLs.

Prodelphinidins isolated from Chinese bayberry leaves induces apoptosis via the p53-dependent signaling pathways in OVCAR-3 human ovarian cancer cells

“…The fractions were collected manually when the target peak was visible on the screen and evaporated under a vacuum. According to our previous results (6), fractions containing dimers and trimers (N2-N7) were considered to be OPAs, which made up almost 23.9% of the PCBLs, whereas fractions containing tetramers and higher polymerizations of proanthocyanidins (N8-N10) were considered to be PPAs and composed almost 47.8% of the PCBLs. The remaining ~30% consisted of epigallocatechin gallate (EGCG), myricetin deoxyhexoside, myricetin deoxyhexoside-gallate, and other polyphenols not detected by normal-phase HPLC/electrospray ionization mass spectrometry.…”

“…According to our previous studies, PCBLs are almost entirely of the galloylated-prodelphinidin type, which is unusual in the plant kingdom as plants normally contain procyanidins and a few prodelphins (6,7). The structural units of prodelphinidins in Chinese bayberry leaves are epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC) and EGCG (6,7). OPAs are fractions collected from preparative HPLC, which mainly contain dimers and trimers including EGC+ECG, EGC+EGCG, 2EGCG, 2ECG, 2EC+EGC, 2EGC+EGCG and 3EGCG.…”

“…PCBLs, OPAs and PPAs, which are all proanthocyanidin extracts, were isolated from Chinese bayberry leaves according to our previous study (6). The finely ground powder of the leaves was extracted with aqueous acetone [acetone:water, 80:20 (v/v)] containing 0.1% (w/v) ascorbic acid at room temperature for 12 h, and was then subjected to rotary-evaporation to remove the acetone.…”

“…A Shimadzu preparative HPLC system (Shimadzu Corporation, Kyoto, Japan) equipped with a CBM-20A module, an SIL-10AP autosampler, an SPD-20A ultraviolet-visible detector and two LC-8A pumps were used. On each run, 1 ml (200 mg/ml) PCBL was applied (6). The fractions were collected manually when the target peak was visible on the screen and evaporated under a vacuum.…”

“…Chinese bayberry leaves are rich in prodelphinidins (6,7). Few studies have been conducted to assess the anticancer effects of prodelphinidins extracted from Chinese bayberry leaves (PCBLs), and the molecular mechanisms underlying the anticancer effect of PCBLs has been minimally investigated in human cancer cells.…”