Antioxidant and Neuroprotective Xenicane Diterpenes from the Brown Alga Dictyota coriacea.

Five new xenicane diterpenes, including three rare nitrogen-containing derivatives, dictyolactams A (1) and B (2) and 9-demethoxy-9-ethoxyjoalin (3), a rare diterpene with a cyclobutanone moiety, named 4-hydroxyisoacetylcoriacenone (4), and 19-O-acetyldictyodiol (5), were isolated from an East China Sea collection of the brown alga Dictyota coriacea, along with 15 known analogues (6-20). The structures of the new diterpenes were elucidated by spectroscopic analyses and theoretical ECD calculations. All compounds had cytoprotective effects against oxidative stress in neuron-like PC12 cells. The antioxidant mechanism of 18-acetoxy-6,7-epoxy-4-hydroxydictyo-19-al (6) was related to the activation of Nrf2/ARE signaling pathway; it also showed significant neuroprotective effects against cerebral ischemia-reperfusion injury (CIRI) in vivo. This study provided xenicane diterpene as a promising lead scaffold for the development of potent neuroprotective agents against CIRI.

Ginsenoside Rg3 suppresses ovarian cancer cell proliferation and invasion by inhibiting the expression of lncRNA H19.

Ovarian cancer (OC) is the most malignant disease of the female reproductive system and accounts for a large proportion of gynecological cancer-related deaths. Emerging evidence has indicated that ginsenoside Rg3, one of the tetracyclic triterpenoid saponins in ginseng, plays crucial roles in regulating cancer progression, yet its role and mechanisms in regulating the proliferation and invasion of OC are still elusive. In this study, the cell viability, proliferation, migration and invasion of OC were assessed by using methyl thiazol tetrazolium (MTT), colony formation, wound healing and Transwell assays, respectively. The protein levels of E-cadherin and N-cadherin were analyzed by Western blot assay. The expression of long noncoding RNA (lncRNA) H19 was analyzed by quantitative real-time polymerase chain reaction (RT-qPCR). The results revealed that ginsenoside Rg3 significantly inhibited the viability of OC cells (SKOV3 and A2780) in a concentration­dependent manner. Ginsenoside Rg3 (50 µg/ml) had almost no significant effect on the activity of human ovarian epithelial cells (HOSEpiCs). Thus, this dose was selected for the subsequent experiments. Furthermore, Rg3 markedly decreased the colony formation, migration and invasion of OC cells. In addition, the expression of N-cadherin was downregulated, and the expression of E-cadherin was upregulated with Rg3 treatment. Moreover, lncRNA H19 was upregulated in OC cells, and Rg3 negatively regulated H19 expression in a concentration-dependent manner. In terms of the mechanism, knockdown of H19 inhibited cell proliferation, migration and invasion, while overexpression of H19 reversed the inhibitory effect of Rg3 on the OC cells. In conclusion, ginsenoside Rg3 suppresses the proliferation, migration and invasion of OC cells by partially inhibiting the expression of lncRNA H19.

Hydroazulene Diterpenes from a Dictyota Brown Alga and Their Antioxidant and Neuroprotective Effects Against Cerebral Ischemia-Reperfusion Injury.

Five new diterpenes, including four new hydroazulenes, (8R,11R)-8,11-diacetoxypachydictyol A (1), (8R*,11R*)-6-O-acetyl-8-acetoxy-11-hydroxypachydictyol A (2), (8R*,11S*)-8-acetoxy-11-hydroxypachydictyol A (3), and (8R*,11S*)-6-O-acetyl-8,11-dihydroxypachydictyol A (4), and a secohydroazulene derivative, named 7Z-7,8-seco-7,11-didehydro-8- acetoxypachydictyol A (5), were isolated from a South China Sea collection of a Dictyota sp. nov. brown alga, together with five known analogues (6-10). Structure elucidation was achieved by extensive spectroscopic analysis and comparison with reported data. All compounds showed potent antioxidant effects against H2O2-induced oxidative damage in neuron-like PC12 cells at a low concentration of 2 µM. The antioxidant property of dictyol C (9) was associated with activation of the Nrf2/ARE signaling pathway; it also showed neuroprotective effects against cerebral ischemia-reperfusion injury (CIRI) in a rat model of transient middle cerebral artery occlusion. As such, hydroazulene diterpenes could serve as lead structures for the development of novel neuroprotective agents against CIRI.

Rapid one-step cleanup method to minimize matrix effects for residue analysis of alkaline pesticides in tea using liquid chromatography-high resolution mass spectrometry.

Matrix effects in complex tea matrices remains a great challenge to rapid quantitative analysis of multi-residue pesticides by analysis of mass spectrometry. Herein, a mixed-mode polymer cationic exchange based dispersive solid-phase extraction (DSPE) procedure was established to eliminate matrix effects of tea for a rapid target alkaline multi-residue pesticides analysis. One-step DSPE procedure can eliminate matrix interferences from the tea extract without additional dilution or tedious cleanup operations. Liquid chromatography-high resolution mass spectrometry using pre-column dilution injection mode was used as the detection technique, while eliminating solvent effects of target analytes and improving the detection sensitivity. Based on this effective analytical method, the results of absolute matrix effects were within 0.77-1.08 for quantitation of the 68 alkaline pesticides, and superior relative matrix effects were also achieved with RSD values below 9.8%. Finally, this method was validated and applied to the alkaline pesticides analysis of the 123 tea samples.

Spongian Diterpenes Including One with a Rearranged Skeleton from the Marine Sponge Spongia officinalis.

Five new diterpenes, including an unprecedented 5,5,6,6,5-pentacyclic diterpene, sponalactone (1), two new spongian diterpenes, 17- O-acetylepispongiatriol (2) and 17- O-acetylspongiatriol (3), and two new spongian diterpene artifacts, 15α,16α-dimethoxy-15,16-dihydroepispongiatriol (4) and 15α-ethoxyepispongiatriol-16(15 H)-one (5), were isolated from a South China Sea collection of the marine sponge Spongia officinalis, together with three known analogues (6-8). The structures of the new diterpenes were elucidated by extensive spectroscopic analysis. The absolute configurations were established on the basis of ECD data. Compounds 1-5 and 7 exhibited moderate inhibition against LPS-induced NO production in RAW264.7 macrophages with IC50 values of 12-32 µM.

A Steroid-Type Antioxidant Targeting the Keap1/Nrf2/ARE Signaling Pathway from the Soft Coral Dendronephthya gigantea.

Four new steroids, named 7-dehydroerectasteroid F (1), 11α-acetoxyarmatinol A (2), 22,23-didehydroarmatinol A (3), and 3-O-acetylhyrtiosterol (4), together with 11 previously described analogues, were isolated from a South China Sea collection of the soft coral Dendronephthya gigantea. The structures of the new steroids were elucidated by comprehensive spectroscopic analysis and by comparison with previously reported data. Compound 1 showed potent protection against H2O2-induced oxidative damage in neuron-like PC12 cells by promoting nuclear translocation of Nrf2 and enhancing the expression of HO-1. 1 represents the first steroid-type antioxidant from marine organisms.