Phytochemistry and pharmacology of natural prenylated flavonoids.

Prenylated flavonoids are a special kind of flavonoid derivative possessing one or more prenyl groups in the parent nucleus of the flavonoid. The presence of the prenyl side chain enriched the structural diversity of flavonoids and increased their bioactivity and bioavailability. Prenylated flavonoids show a wide range of biological activities, such as anti-cancer, anti-inflammatory, neuroprotective, anti-diabetic, anti-obesity, cardioprotective effects, and anti-osteoclastogenic activities. In recent years, many compounds with significant activity have been discovered with the continuous excavation of the medicinal value of prenylated flavonoids, and have attracted the extensive attention of pharmacologists. This review summarizes recent progress on research into natural active prenylated flavonoids to promote new discoveries of their medicinal value.

Cucurbitane-type triterpenoids from the fruits of Citrullus colocynthis.

A phytochemical investigation of the fruits of Citrullus colocynthis resulted in the isolation of 21 structurally diverse cucurbitane triterpenoids, including 9 previously undescribed ones, colocynins A-I (1-9). Their absolute configurations were elucidated by means of quantum chemical electronic circular dichroism (ECD) calculations, CD exciton chirality method, and single-crystal X-ray crystallography. Colocynins A-C (1-3) represent the first examples of nonanorcucurbitane-type triterpenoids. An anti-acetylcholinesterase activity assay showed that 6, 10, 13, 18, and 20 exhibited inhibitory activities, with IC50 values ranging from 5.0 to 21.7 µM. In addition, 18 and 21 showed significant cytotoxicity against PACA, A431, and HepG2 cells, with IC50 values ranging from 0.042 to 0.60 and 3.6-14.4 µM, respectively.

Two new nor-lignans from Selaginella pulvinata (Hook. & Grev.) Maxim and their antihyperglycemic activities.

Two new nor-lignans, pulvin A (1) and moellenoside C (2), along with two known compounds (3-4) were isolated from the whole plant of Selaginella pulvinate (Hook. & Grev.) Maxim. The structures of the new compounds were established on the basis of spectroscopic data and acid hydrolysis. All the isolates were investigated for their antihyperglycemic activities in 3T3-L1 adipocytes. The results showed that compounds 1 and 2 promoted the glucose consumption prominently in 3T3-L1 adipocytes in a dose-response manner. Compound 1 and 2 induced 1.14-1.73 folds and 1.03-1.55 folds changes relative to the basal level, respectively, in the concentration range of 12.5 µM to 50 µM.

neo-Clerodane diterpenoids from the aerial parts of Teucrium fruticans cultivated in China.

Seven neo-clerodane diterpenes, teufruintins A-G (1-7), together with eight known compounds (8-15) were isolated from the CHCl3-soluble fraction of the aerial parts of Teucrium fruticans cultivated in China. The chemical structures of the isolated compounds were elucidated using different spectroscopic methods. All of the isolated diterpenes were evaluated for their cytotoxic activities on three human cancer cell lines, and for their ability to inhibit LPS-induced nitric oxide production in RAW 264.7 macrophages. None of the compounds displayed cytotoxic activities on the cancer cell lines, and only 15 showed weak NO inhibitory activity.

Teucvisins A-E, five new neo-clerodane diterpenes from Teucrium viscidum.

Two new neo-clerodane diterpenoids, teucvisins A and B (1, 2), and three new 19-nor-neoclerodane diterpenoids, teucvisins C-E (3-5), together with ten known constituents (6-15) were isolated from the whole plants of Teucrium viscidum. All the isolates were evaluated for their inhibitory activities of lipopolysaccharide (LPS)-induced nitric oxide production in RAW264.7 macrophages. The results indicated that compounds 11 and 15 showed moderate inhibition with an IC50 value of 21.9 and 22.4 µM, respectively.

Antihyperglycemic glucosylated coumaroyltyramine derivatives from Teucrium viscidum.

Eight new glucosylated coumaroyltyramine derivatives, teuvissides A-H (1-8), were isolated from whole plants of Teucrium viscidum. Their structures were elucidated using spectroscopic data and chemical methods. The antihyperglycemic activities of these compounds were evaluated in HepG2 cells and 3T3-L1 adipocytes, and all of the isolates elicited different levels of glucose consumption at a concentration of 2.0 µM. Teuvissides A (1), B (2), and F (6) induced 2.2-, 2.1-, and 2.2-fold changes, respectively, in the levels of glucose consumption in HepG2 cells and 2.5-, 2.1-, and 2.3-fold changes, respectively, in 3T3-L1 adipocytes relative to the basal levels.