3,4-seco-28-Nor-oleanane triterpenes from Camellia japonica protect from neurotoxicity in a rotenone model of Parkinson's disease

Polyphenolic Glycosides from the Fruits Extract of Lycium ruthenicum Murr and Their Monoamine Oxidase B Inhibitory and Neuroprotective Activities

The fruits ofLycium ruthenicum Murr have long been consumed as health food and used in folk medicine in China. Apart from the well-known polysaccharides, the active small molecular constituents in this fruit have not been fully studied. In this work, a systematic phytochemical study was carried out to investigate the small molecules and their potential health benefits. Nine new polyphenolic glycosides, lyciumserin A-I (1-9), together with 16 known compounds (10-25), were isolated and elucidated by high-resolution electrospray ionization mass spectrometry and comprehensive NMR analyses in combination with chemical hydrolysis. Compounds 1, 2, and 16 exhibited moderate inhibitory activity of monoamine oxidase B (MAO-B), while compounds 1 (50 μM) and 2 (100 μM) displayed significant neuroprotective effects (69.22 and 72.38% of cell viability, respectively) in the 6-hydroxydopamine-induced injury of the PC12 cell model (54.41%), comparable to the positive drug rasagiline (70.45%). The neuroprotective effect of 1 and 2 was further evidenced by the observation of the morphological change and fluorescein diacetate/propidium iodide staining. In addition, the levels of the major active compounds (1, 3, 5/6, and 16-18) vary from 21.5 to 892.3 μg/g. This is the first report on phenolic glycosides from the fruits ofL. ruthenicum Murr that possess both significant MAO-B inhibitory and neuroprotective effects, indicating the promising potential of the fruits for the development of health care products and even therapeutic agents for the treatment of Parkinson's disease and other neurodegenerative diseases.

Neuroprotective Effects of Triterpenoids from Camellia japonica against Amyloid β-Induced Neuronal Damage

Alzheimer's disease (AD), a neurocognitive impairment affecting human mental capacity, is related to the accumulation of amyloid-β peptide (Aβ) and the hyperphosphorylation of tau protein. In addition to modern therapies approved for AD treatment, natural products with antioxidant and anti-inflammatory properties have been studied for their potential to prevent AD pathogenesis. Six new noroleanane triterpenoids from the fruit peels of Camellia japonica were isolated, and their structures were determined by diverse spectroscopic methods. The neuroprotective effects of the six new compounds were tested against Aβ-induced neurotoxicity and neuroinflammation in mouse hippocampal and microglial cells. In the model of HT22-transfected cells, compounds 1-4 showed strongly neuroprotective effects via antioxidant response element gene activation and decreased the level of glutamate uptake. Compounds 1-4 also appeared to have strong inhibitory effects on NO production in Aβ_1-42-transfected BV2 microglial cells. A docking simulation study was used to explain the inhibitory effects of compounds 1-4 on β-secretase 1 (BACE1). Noroleanane triterpenoids 1-4 had potential neuroprotective and anti-inflammatory effects against Aβ-induced neuronal damage. The structure-activity relationships of the 30 oleanane triterpenoids from C. japonica were assessed in a model of Aβ_1-42-transfected HT22 cells.

Prophylactic and therapeutic roles of oleanolic acid and its derivatives in several diseases

Oleanolic acid (OA) and its derivatives are widely found in diverse plants and are naturally effective pentacyclic triterpenoid compounds with broad prophylactic and therapeutic roles in various diseases such as ulcerative colitis, multiple sclerosis, metabolic disorders, diabetes, hepatitis and different cancers. This review assembles and presents the latest in vivo reports on the impacts of OA and OA derivatives from various plant sources and the biological mechanisms of OA activities. Thus, this review presents sufficient data proposing that OA and its derivatives are potential alternative and complementary therapies for the treatment and management of several diseases.

Plant triterpenoids with bond-missing skeletons: biogenesis, distribution and bioactivity

Covering: up to December 2018 The polycyclic ABCD(E) framework of triterpenoids can miss a single endocyclic C-C bond as a result of a modification of the cyclization cascade that triggers their formation (interrupted- or diverted cascades), or can be the result of post-cyclization ring cleavage by late-stage oxidative modifications (seco-triterpenoids). Because of mechanistic and biogenetic differences, ring opening associated with loss of a skeletal fragment, as in nor-seco-triterpenoids (limonoids, quassinoids), will not be covered, nor will compounds where ring opening is part of a fragmentation cascade or of a multiple diversion from it. Even with these limitations, 342 bond-missing triterpenoids could be retrieved from the literature, with transversal distribution in the plant kingdom. Their structural diversity translates into a variety of biological targets, with dominance of potential applications in the realm of cancer, neuroprotection, and anti-infective therapy. In addition to the bioactivity and chemotaxonomic relevance of bond-missing triterpenoids, current knowledge on the genetic basis of interrupted- and diverted oxidosqualene cyclases will be summarized. This untapped source of enzymes could be useful to selectively modify triterpenoids by metabolic engineering, circumventing the bottlenecks of their isolation (poor yield or inadequate supply chain) to explore new areas of their chemical space.