Dihydro-β-agarofuran sesquiterpenoid derivatives with neuroprotective activity from the leaves of Tripterygium wilfordii

Neurotrophic Natural Products

Neurotrophins (NGF, BDNF, NT3, NT4) can decrease cell death, induce differentiation, as well as sustain the structure and function of neurons, which make them promising therapeutic agents for the treatment of neurodegenerative disorders. However, neurotrophins have not been very effective in clinical trials mostly because they cannot pass through the blood-brain barrier owing to being high-molecular-weight proteins. Thus, neurotrophin-mimic small molecules, which stimulate the synthesis of endogenous neurotrophins or enhance neurotrophic actions, may serve as promising alternatives to neurotrophins. Small-molecular-weight natural products, which have been used in dietary functional foods or in traditional medicines over the course of human history, have a great potential for the development of new therapeutic agents against neurodegenerative diseases such as Alzheimer's disease. In this contribution, a variety of natural products possessing neurotrophic properties such as neurogenesis, neurite outgrowth promotion (neuritogenesis), and neuroprotection are described, and a focus is made on the chemistry and biology of several neurotrophic natural products.

First Report on Inhibitory Effect against Osteoclastogenesis of Dihydro-β-agarofuran-Type Sesquiterpenoids

Dihydro-β-agarofuran-type sesquiterpenoids are characteristic metabolites of Celastraceae plants, and the extracts of these plants have been developed into botanical pesticides. In the course of our efforts to find novel natural biologically active products, eight new dihydro-β-agarofuran-type sesquiterpenoids (1-8) were identified from the stems of Celastrus monospermus Roxb. Their structures were elucidated by extensive spectroscopic analysis, single crystal X-ray crystallography, and electronic circular dichroism (ECD) calculations. In consideration of the efficacy of certain Celastrus plants for the treatment of arthritis and arthralgia in folk medicine, the isolates were evaluated for their inhibitory activities against osteoclastogenesis. As a result, compounds 4, 6, and 7 were found to restrain osteoclastogenesis induced by receptor activator of nuclear factor-κB ligand (RANKL) with IC₅₀ values of 0.58, 1.2, and 6.1 μM, respectively. Furthermore, compound 4 was found to inhibit osteoclastogenesis-related gene (c-Fos, MMP-9, CTSK, TRAP) expression and block c-Fos protein expression and inhibited bone resorption of mature osteoclasts induced by M-CSF and RANKL in a dose dependent manner. This is the first report of dihydro-β-agarofuran-type sesquiterpenoid for their potential medical applications in bone metabolic diseases.

Natural Nitrogenous Sesquiterpenoids and Their Bioactivity: A Review

Nitrogenous sesquiterpenoids fromnatural sourcesare rare, so unsurprisingly neither the potentially valuable bioactivity nor thebroad structural diversity of nitrogenous sesquiterpenoids has been reviewed before. This report covers the progressduring the decade from 2010 to February 2020 on the isolation, identification, and bioactivity of 391 nitrogen-containing natural sesquiterpenes from terrestrial plant, marine organisms, and microorganisms. This complete and in-depth reviewshouldbe helpful for discovering and developing new drugs of medicinal valuerelated to natural nitrogenous sesquiterpenoids.