The leaves of Apocynum venetum L. (AV), a native Chinese plant, have been used as folk medicine in China and Japan. This study evaluated the content of the active antioxidant component and antioxidant activities of AV, and its two alternative species, Poacynum pictum (Schrenk) Baill. (PP) and Poacynum hendersonii (Hook.f.) Woodson (PH). The total phenolic and total flavonoid contents were determined. In addition, the quantitative analysis of two major flavonoid compounds (hyperoside and isoquercitrin) was carried out by HPLC. The antioxidant activities were investigated by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity method, the reducing power test and the chelating ability of ferrous ions. The highest total phenolic and flavonoid contents were observed in the AV methanolic extract, followed by the PP and PH methanolic extracts. HPLC analysis indicated that isoquercitrin was one of the major components in all three species, however, hyperoside was only detected in AV at high levels. All the antioxidant assays we performed demonstrated that the AV extract was markedly superior to those of the other two species.

In this study, the effects of Peucedanum praeruptorum DUNN methanolic extract (PPME) and its major constituents on SGC7901 human gastric cancer cells were evaluated. Two pyranocoumarins, namely, (±) praeruptorin A (PA) and (±) praeruptorin B (PB), were isolated from PPME. A high performance liquid chromatographic (HPLC) method was developed to determine the contents of PA and PB in PPME. The antiproliferative and cytotoxic actions of PPME were observed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and release of lactate dehydrogenase (LDH) assays. At 300 µg/mL, PPME inhibited cell growth by 51.2% (P < 0.01), probably linked to the high concentration of PA and PB. Both PA and PB exhibited antiproliferative and cytotoxic activities on the SGC7901 cells. Furthermore, the active principle compound, PA, also enhanced the actions of doxorubincin (DOX) on SGC7901 cells. Cell growth decreased higher with the combined treatment of PA and DOX than that with the chemotherapy agent applied alone, suggesting that PA could reduce the dose of DOX for the desired effects.

Four new p-aminoacetophenonic acids, named (2E)-11-(4′-aminophenyl)-5,9-dihydroxy-4,6,8-trimethyl-11-oxo-undec-2-enoic acid (1), 9-(4′-aminophenyl)-3,7-dihydroxy-2,4,6-trimethyl-9-oxo-nonoic acid(2), (2E)-11-(4′-aminophenyl)-5,9-O-cyclo-4,6,8-trimethyl-11-oxo-undec-2-enoic acid (3) and 9-(4′-aminophenyl)-3,7-O-cyclo-2,4,6-trimethyl-9-oxo-nonoic acid(4), were isolated from an endophyte Streptomyces sp. (strain HK10552) of the mangrove plant Aegiceras corniculatum. The structures of 1–4 were elucidated by using spectroscopic analyses. The relative stereoconfigurations of compounds 3 and 4 were determined by NOESY experiments. In the bioassay test, 1–4 showed no cytotoxicity against the Hela cell lines. Compound 4 also showed no inhibitory bioactivity on HCV protease and SecA ATPase and wasn’t active against VSVG/HIV-luc pseudotyping virus.