Seed shells of the Japanese horse chestnut (Aesculus turbinata BLUME) contain high levels of polyphenolic antioxidants. These compounds were extracted, fractionated, and finally separated into three fractions, F1, F2, and F3, according to their degrees of polymerization. The structures of the isolated fractions were characterized by a combination of mass spectrometric analyses. F1 contained mainly low molecular weight phenolic substances, including procyanidin trimers. The predominant fractions F2 and F3 consisted of polymeric proanthocyanidins having a series of heteropolyflavan-3-ols, (+)-catechin/(-)-epicatechin units, and polymerization degrees of 19 and 23, respectively. The polyphenol polymers had doubly linked A-type interflavan linkages in addition to single B-type bonds without gallic acid esterified to them. The isolated polyphenolic compounds exhibited potent antioxidative activities comparable to monomeric (+)-catechin and (-)-epicatechin, or more efficacious than those monomers. The results suggest the potential usefulness of polyphenol polymers from seed shells as a source for nutraceutical factors.

The study of the chemical constituents of branches and twigs of collected in Singapore led to the isolation and structural elucidation of four new xanthones, named cratoxanthone A (), B (), C (), and D (), together with six known xanthones (-) and one known dihydroanthracenone (). Eight xanthones (including and) and were tested for their antiproliferative activity in three human carcinoma cell lines (lung adenocarcinoma A549, colorectal carcinoma Colo205, and epidermoid carcinoma KB) and a human acute lymphoblastic leukemia B cell line (NALM-6), and the mitochondrial membrane potential was determined in KB cells. New xanthones and attenuated NALM-6 cell proliferation with IC values of 17.78 and 8.27 µM, respectively. Furthermore, KB cells treated with these compounds had significantly decreased mitochondrial membrane potentials. Notably, the proliferation of A549 cells was specifically inhibited by , but not the xanthones.

Seed shells are discarded as waste products of Japanese horse chestnut seeds used as ingredients in traditional Japanese foods. Hot-water extraction of these seed shells yielded substances that were tested