Characterization of Unusual Proanthocyanidins in Leaves of Bayberry (Myrica rubra Sieb. et Zucc.)

Abstract

Extractable and unextractable proanthocyanidins (EPAs and UEPAs) from leaves of bayberry were characterized. Both EPAs and UEPAs were analyzed by acid catalysis in the presence of excess phloroglucinol. The main cleavage product, epigallocatechin-3-O-gallate-(4β→2)-phloroglucinol, was successfully identified. The EPAs were of the prodelphinidin type. In fact, epigallocatechin-3-O-gallate (EGCG) and traces of epigallocatechin (EGC) were detected as the extension units, but only EGCG was present in the terminal units. All of the compounds exhibited a 2,3-cis configuration, and >98% of them were galloylated. The mean degree of polymerization (mDP) of bayberry leaf EPAs was 6.5, and the most abundant EPAs were the polymers, with mDP values of 9.5−26.7. The UEPAs were highly polymerized prodelphinidins consisting of EGCG and traces of EGC. In addition, EGCG, three EPA dimers, and two trimers were identified. The EPAs and UEPAs consisted mostly of EGCG, which is unusual in the plant kingdom.

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

“…A previous study based on thiolytic degradation with phloroglucinol has shown that PCBLs are essentially of the prodelphinidin type, and more than 98% of them were galloylated [21]. The 13 C NMR spectrum of the crude bayberry PAs (Figure 2) has the characteristic features of a mixed PA with 3-O-galloylation on some subunits [26].…”

“…Extraction and purification of PAs from Chinese bayberry leaves were carried out essentially according to our previous procedures [21]. In brief, the leaves were dried at 40°C for 12 h and then ground well into a powder by milling.…”

“…leaves are limited. Masuda et al identified two monomers (EGC and EGCG)[20]; Yang et al identified five flavan-3-ol monomers (EGCG) and oligomeric PAs (EGC-EGCG, 2EGCG, 2EGCG+EGC and 3EGCG), and elucidated the structural features of bayberry leaf PAs by using acidic degradation [21].…”

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

“…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.…”

“…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.…”