Polyphenols in twenty cultivars of blue honeysuckle (Lonicera caerulea L.): Profiling, antioxidant capacity, and α-amylase inhibitory activity

The polyphenols extracted from 20 blue honeysuckle cultivars were comprehensively characterized and quantified by HPLC-DAD and HPLC-ESI-QTOF-MS2 analyses and evaluated for antioxidant capacity (ABTS, DPPH, FRAP) and α-amylase inhibitory activity. The 17 anthocyanins and 59 non-anthocyanin phenolics were characterized. Among them, cyanidin-3-glucoside, quercetin-3-galactoside, myricetin-3-galactoside, and 3-caffeoylquinic acid were the major polyphenols. These polyphenols not only contributed to the antioxidant capacity, but were also good α-amylase inhibitors. 'Lanjingling' showed the strongest antioxidant capacity evaluated by FRAP, while 'CBS-2' and '14-13-1' showed the strongest antioxidant capacity evaluated by ABTS and DPPH. All the twenty cultivars showed α-amylase inhibitory activity, and the IC50 values ranged from 0.12 ± 0.01 to 0.69 ± 0.02 mg/mL. 'Lanjingling' showed the most potent α-amylase inhibitory activity. Additionally, principal component analysis indicated that Lonicera. caerulea subsp. emkuyedao bred in Japan differed markedly in phenolics and bioactivity compared to the other four subspecies bred in China and Russia.