Terpenoids with α-glucosidase inhibitory activity from Rhododendron minutiflorum Hu

Five undescribed triterpenoids, two unusual omphalane-type sesquiterpenoids together with twenty-five known compounds were isolated from the leaves and stems of Rhododendron minutiflorum Hu. The absolute configurations of 1-3 and 6 were established by single-crystal X-ray diffraction analysis and electronic circular dichroism (ECD). Compounds 6-7 feature the rare omphalane-type sesquiterpene skeleton and are verified by single-crystal X-ray diffraction analysis for the first time. In the biological activity assay, most of the triterpenoids have different degrees of inhibitory effects on α-glucosidase, with IC₅₀ values ranging from 6.97 to 229.3 μM (the positive control drug acarbose has an IC₅₀ value of 3.07 × 10^-3 μM). Structure and activity relationship (SAR) study reveals that the oxidation degrees of C-3, C-8, or C-11 to C-13 of the ursane-type triterpenoid influence the inhibitory activity dramatically.

Plant Derived Natural Products against Pseudomonas aeruginosa and Staphylococcus aureus: Antibiofilm Activity and Molecular Mechanisms

Bacteria are social organisms able to build complex structures, such as biofilms, that are highly organized surface-associated communities of microorganisms, encased within a self- produced extracellular matrix. Biofilm is commonly associated with many health problems since its formation increases resistance to antibiotics and antimicrobial agents, as in the case of Pseudomonas aeruginosa and Staphylococcus aureus, two human pathogens causing major concern. P. aeruginosa is responsible for severe nosocomial infections, the most frequent of which is ventilator-associated pneumonia, while S. aureus causes several problems, like skin infections, septic arthritis, and endocarditis, to name just a few. Literature data suggest that natural products from plants, bacteria, fungi, and marine organisms have proven to be effective as anti-biofilm agents, inhibiting the formation of the polymer matrix, suppressing cell adhesion and attachment, and decreasing the virulence factors' production, thereby blocking the quorum sensing network. Here, we focus on plant derived chemicals, and provide an updated literature review on the anti-biofilm properties of terpenes, flavonoids, alkaloids, and phenolic compounds. Moreover, whenever information is available, we also report the mechanisms of action.

Anti-breast-Cancer Activity Exerted by β-Sitosterol-d-glucoside from Sweet Potato via Upregulation of MicroRNA-10a and via the PI3K-Akt Signaling Pathway

Breast cancer (BC) is a prominent source of cancer mortality in women throughout the world. β-Sitosterol-d-glucoside (β-SDG), a newly isolated phytosterol from sweet potato, possibly displays potent anticancer activity. However, the probable anticancer mechanisms involved are still unclear. This study sought to study how β-SDG from sweet potato affects two BC cell lines (MCF7 and MDA-MB-231) and nude mice bearing MCF7-induced tumors. In addition, we assessed how β-SDG affects tumor suppressor miR-10a and PI3K-Akt signaling in BC cells. Cell viability and proliferation were determined via MTT and colony-formation assays, and apoptosis was quantified by Hoechst staining and flow cytometry. In addition, miR-10a expression and apoptosis-related protein levels were measured. Our study indicated that β-SDG exhibited cytotoxic activities on MCF7 and MDA-MB-231 cells via inducing apoptosis and activating caspase proteases in these cells. Furthermore, the experimental results in nude mice bearing MCF7-induced tumors demonstrated that oral β-SDG administration at medium (60 mg/kg) or high (120 mg/kg) doses was sufficient to substantially impair the growth of tumors and to decrease the levels of CEA, CA125, and CA153 by 64.71, 74.64, and 85.32%, respectively, relative to those of the controls ( P < 0.01). β-SDG was further found to regulate the expression of PI3K, p-Akt, Bcl-2-family members, and other factors involved in the PI3K-Akt-mediated mitochondrial signaling pathway via the tumor suppressor miR-10a. These findings indicated that β-SDG suppresses tumor growth by upregulating miR-10a expression and inactivating the PI3K-Akt signaling pathway. Furthermore, β-SDG could be developed as a potential therapeutic agent against MCF7-cell-related BC.