The Chemical Constituents from Fruits of Catalpa bignonioides Walt. and Their α-Glucosidase Inhibitory Activity and Insulin Secretion Effect.

Catalpa pod has been used in traditional medicine for the treatment of diabetes mellitus in South America. Studies on the constituents of Catalpa species have shown that it is rich in iridoids. In the present study, three previously undescribed compounds (2-4), including two secoiridoid derivatives along with twelve known compounds, were isolated from the fruits of Catalpa bignonioides Walt. In addition, fully assigned 13C-NMR of 5,6-dihydroxy-7,4'-dimethoxyflavone-6-O-sophoroside (1) is reported for the first time in the present study. The structures of compounds were determined on the basis of extensive spectroscopic methods, including UV, IR, 1D, and 2D NMR, mass spectroscopy, and CD spectroscopic data. All the isolated compounds were evaluated for α-glucosidase inhibitory activity. Among the tested compounds, compounds 2, 3, and 9 exhibited significant inhibitory activity against α-glucosidase enzyme assay. Meanwhile, the effect of compounds 2, 3, and 9 on glucose-stimulated insulin secretion (GSIS) was measured using pancreatic ß-cells. Compounds 2, 3, and 9 exhibited non-cytotoxicity-stimulated insulin secretion in INS-1 cells. The expression levels of proteins associated with ß-cell function and insulin secretion such as phosphorylation of total insulin receptor substrate-2 (IRS-2), phosphatidylinositol 3-kinase (PI3K), Akt, activated pancreatic duodenal homeobox-1 (PDX-1), and peroxisome proliferator-activated receptor-γ (PPAR-γ) were increased in INS-1 cells after treatment with compounds 2, 3, and 9. The findings of the present study could provide a scientific warrant for their application as a potential antidiabetic agent.

Chemical constituents from the fruits of Schisandra sphenanthera and their cytotoxicity activity

Abstract Schisandra sphenanthera Rehder & E.H. Wilson, Schisandraceae, is well known as a type of traditional medicine for the treatment of hepatitis, diarrhea and insomnia in Asia. It was also reported to have antiviral and anti-HIV activities. Using various chromatographic resins and isolation techniques, a new lignan (1), erythro-4-(3,4-dimethoxyphenyl)-4-hydroxy-3-methylbutan-2yl-3,4-dimethoxybenzoate, along with fifteen known compounds, were isolated from fruits of S. sphenanthera. The structures of the compounds were identified by extensive spectroscopic and spectrometric methods including 1D and 2D NMR and MS data. All the isolated compounds were evaluated for their cytotoxicity activity against Hela, HepG2 and HCT-116 cells. Among them, compound schisanlactone C showed significant cytotoxicity activity.

Neuraminidase inhibitory activity by compounds isolated from aerial parts of Rhinacanthus nasutus.

Rhinacanthus nasutus (L.) Kurz (Acanthaceae) is known as traditional medicine for the treatment of various diseases, such as cancer, fungal infections, herpes virus infections and several types of skin diseases in South-East Asian countries. In this study, eight compounds 1-8 were isolated from the aerial parts of R. nasutus. The structures of compounds were determined by the spectroscopic methods, including 1D and 2D NMR. The isolated compounds were evaluated for neuraminidase inhibitory activity. Several lignans, 2,3-bis[(4-hydroxy-3,5-dimethoxyphenyl)methyl]-1,4-butanediol (5) and 8,8'-bisdihydrosiringenin glucoside (6), significantly inhibited neuraminidase activity, which was comparable to the positive controls, mangiferin and oseltamivir. In addition, a structure-based virtual screening against neuraminidase using bioactive components was demonstrated.