Abstract Dried unripe raspberries (Rubus chingii), a kind of Chinese herbal medicine, have been used for many years in China. They were prepared as unpurified raspberry extract (URE) by ethanol extraction, and purified raspberry extract (PRE) by macroporous resin. Synergistic effects between the URE (or the PRE) and ampicillin, erythromycin, tetracycline or streptomycin against Escherichia coli, Staphylococcus aureus and Salmonella enterica were carried out using checkerboard microdilution and time-kill curves, respectively. The results showed that all pairwise combinations revealed synergistic effects, with 0.10 ≤ fractional inhibitory concentration index ≤ 0.50 and more than 2 × log10 reduction in colony-forming units/mL. In particular, the erythromycin concentration in the combinations was reduced to 1/50-1/100 of its dose alone while retaining its effectiveness against S. aureus and E. coli. The synergistic effects of raspberry extracts and four antibiotics against three bacteria were related to the abundance of polyphenols in the extracts, especially ellagic acid. The extracts may be a dietary supplement and/or natural antimicrobials.

Abstract Twelve typical polyphenols in raspberry leaf powder (RLP), raspberry leaf extract 1 (RLE) and raspberry leaf extract 2 (RLE-H) were analyzed by HPLC-MS. The sum of their contents in three samples were in the following order: RLP (8.6 mg g-1) < RLE (35.0 mg g-1) < RLE-H (44.1 mg g-1). Ellagic acid and quercetin-3-O-glucuronide were the principal compounds in the samples and accounted for more than 75% of the sum content. A gelled mixture of RLE, pectin, and sodium alginate administrated to mice via gavage resulted in reduced weight gain and adiposity percentage, increased teste percentage, prolonged exhaustion time, furthermore alleviated intestinal flatulence possibly induced by RLE or RLE-H alone. These results could help in making rational use of this high polyphenol extract from raspberry leaves.

Abstract Dried unripe raspberry of Rubus chingii, were prepared as the following four extracts: unpurified raspberry extract (URE), purified raspberry extract (PRE), URE after high temperature-high pressure (UPE-H, HTHP), and PRE after HTHP (PRE-H). The total polyphenolic contents (TPCs) and total flavonoid contents (TFCs) of the four extracts, as assessed by colorimetry, significantly increased in the following order: URE < URE-H < PRE < PRE-H. The antioxidant capacity and antibacterial activity were as follows: PRE-H > PRE ≈ URE-H > URE. Moreover, 11 typical polyphenols were quantified using a HPLC-MS analysis showed that HTHP treatments were conducive to releasing more (+)-catechin, (−)-epicatechin, proanthocyanidin B1 and ellagic acid, reaching ~70% ‒1,100%, but decreased the rutin, quercetin-3-O-glucuronide, kaempferol-3-O-rutinoside and kaempferol-3-O-glucoside levels by ~10% –20%. The purification of macroporous resin was beneficial to the enrichment of all polyphenols, by ~30%–300%. Ellagic acid was the main polyphenol found in the extracts, accounting for ~67%-74%. The study indicated that changes in the polyphenols of raspberry extracts after resin purification and/or HTHP treatment were correlated with the extract’s antioxidant capacity and antibacterial activity. Further evaluations of the correlation between bioactive ingredients and treatments should reveal that HTHP and resin purification methods are effective means of preparing extracts.