Among polyphenol compounds, the flavan-3-ol structure, which is the basic unit of green tea catechins and the galloyl groups contained in green tea catechins are known to exhibit various functions. In this paper, we discuss how to concentrate highly functional polyphenol compounds by exploiting the interaction between gelatin and the catechol structures. First, we confirmed the interaction between heat-stabilized gelatin and flavan-3-ol derivatives, including synthesized compounds. When green tea leaf extract containing a large amount of flavan-3-ol derivatives was incubated with gelatin, most of the polyphenol compounds it contained were adsorbed. Because the compounds adsorbed on gelatin could not be eluted, DPPH radical and ABTS radical scavenging activity tests were conducted using the as-prepared gelatin–polyphenol complex. Radical scavenging activity was observed when the compounds were adsorbed on gelatin and heating at 90 °C for 5 min did not have a significant effect on their activity. These results suggest that functional polyphenols can be efficiently concentrated using heat-stabilized gelatin and retain their functionality while adsorbed.

Flavan-3-ol derivatives are polyphenolic compounds with multifunctional properties. One of the flavan-3-ol derivatives, green tea catechin epigallocatechin gallate, is known to have anticancer activity as one of its multifunctional properties. We have studied the synthesis of flavan-3-ol derivatives and conducted structure-activity relationship studies; we found that the fluorinated derivatives exhibited high toxicity against HeLa and A549 cells. It was confirmed that the cytotoxicity was affected by the conformation of the flavan-3-ol skeleton and that the 2,3-cis form was dominant. The addition of fluorinated compounds increased the amount of intracellular mitochondrial superoxide, abolished the membrane potential of mitochondria, and, interestingly, formed granular aggregates containing mitochondria. When the level of LC3-II, a marker of autophagy induction, was confirmed, it suggested that the addition of the fluorinated compounds promoted autophagy. These results suggest that the novel highly cytotoxic fluorinated flavan-3-ol compound synthesized in this study promotes autophagy and induces cell death by triggering mitochondrial dysfunction. We believe that these results suggest the possibility of conferring more functionality through structural transformations of flavan-3-ol derivatives.

Inspired by the potential functional activity of polyphenol compounds contained in raspberry (Rubus idaeus), we previously explored the effects of the cultivation environment and maturity on the polyphenolic profiles of raspberry leaves and fruits. Herein, building on our previous studies, we used high-performance liquid chromatography and liquid chromatography–mass spectrometry to profile the polyphenol compounds contained in five parts of raspberry flowers (receptacles, sepals, pistils, stamens, and petals), revealing the presence of (+)-catechin, (−)-epicatechin, procyanidin B4, procyanidin C3, sanguiin H-6, and lambertianin C in all flower parts. Petals also contained (−)-epicatechin-3,5-di-O-gallate, kaempferol-7-O-glucoside, and naringenin-7-O-glucoside as well as other flavan-3-ol derivatives efficiently scavenging free radicals and inhibiting the growth of cancer (HeLa S3) cells. Thus, raspberry flower petals were concluded to be a good source of characteristic and highly functional flavan-3-ol derivatives.