PMC

The structures of flavan-3-ol derivatives contained in raspberry.

Structures of hydrolysable tannins contained in leaves of red raspberry.

Partial schematic representation of flavonoid biosynthesis. CHS: chalcone synthase; F3′H: flavonoid 3′-hydroxylase; FLS: flavonol synthase; DFR: dihydroflavonol 4-reductase; ANS: anthocyanin synthase; and LAR: leucoanthocyanidin reductase.

HPLC chromatograms of leaf extracts obtained from raspberry plants cultivated under condition A to H. Peak numbers are: 1: (+)-catechin; 2: (–)-epicatechin; 3: procyanidin B4; 4: flavan-3-ol trimer; 5: 1-galloylpedunculagin; 6: sanguiin H-6; and 7: lambertianin C.

Expression level of flavan-3-ol biosynthesis enzyme encoding genes in raspberry leaves under conditions A, B, C, D, and F. Total RNA was extracted from fresh leaves after 7 days LED light irradiation treatment and used for sqRT-PCR analysis.

Total polyphenol and proanthocyanidin under different LED light treatment. (a) Total polyphenols were determined by the Folin–Ciocalteu method. Data are mg of gallic acid equivalent per 100 mg/mL DMSO solution of raspberry leaf extract; and (b) total proanthocyanidin was determined by a modified protein precipitation method. Data are mg of procyanidin B2 equivalent per 100 mg/mL DMSO solution of raspberry leaf extract. Error bars represent SD of the mean (n = 4).

Radical scavenging activity in raspberry leaf extracts. (a) DPPH radical scavenging activity; one mL of 30 μM DPPH solution in EtOH was added to 1 μL of raspberry leaf extract in DMSO solution for a final concentration of 1, 5, or 10 μg/mL. Vitamin E was used as a control. Error bars represent standard deviation of the mean (n = 8); and (b) ABTS radical scavenging activity; one mL of diluted ABTS solution (absorbance at 740 nm = 0.70 ± 0.02) was added to 1 μL of raspberry leaf extract in DMSO solution for a final concentration of 1, 5, or 10 μg/mL. (+)-Catechin was used as a control. Error bars represent standard deviation of the mean (n = 8).