Bioactive icetexane and abietane diterpenes from Isodon phyllopodus.

A new icetexane diterpenoid, 11, 12, 20α-trihydroxyl-7ß-methoxyicetexa-8, 11, 13-triene-19, 10-lactone [Phyllane A (1)], and a new abietane diterpenoid, 7ß, 20-epoxy-3ß, 17-acetoxy-abieta-8, 11, 13-teriene-11, 12-diol [phyllane B (2)], along with two known compounds (3 and 4) were isolated from the methanol (MeOH) extract of twigs and leaves of the folk medicinal Isodon phyllopodus. Their structures were determined by spectroscopic analyses including 2 D NMR spectral data, and further confirmed by X-ray single crystal diffraction. Moreover, the compounds were evaluated for their cytotoxicity and anti-HIV activities, and phyllane A showed anti-HIV activity with an IC50 value of 15.7 µM, but phyllane B was found to be cytotoxic to the A549 host cells with a CC50 value of 108.5 µM.

3,4-Seco-Isopimarane Diterpenes from the Twigs and Leaves of Isodon Flavidus.

Three isopimarane diterpenes [fladins B (1), C (2), and D (3)] were isolated from the twigs and leaves of Chinese folk medicine, Isodon flavidus. The chemical structures were determined by the analysis of the comprehensive spectroscopic data, and the absolute configuration was confirmed by X-ray crystallographic analysis. The structures of 1-3 were formed from isopimaranes through the rearrangement of ring A by the bond break at C-3 and C-4 to form a new δ-lactone ring system between C-3 and C-9. This structure type represents the first discovery of a natural isopimarane diterpene with an unusual lactone moiety at C-9 and C-10. In the crystal of 1, molecules are linked to each other by intermolecular O-H···O bonds, forming chains along the b axis. Compounds 1-3 were evaluated for their bioactivities against different diseases. None of these compounds displayed cytotoxic activities against HCT116 and A549 cancer cell lines, antifungal activities against Trichophyton rubrum and T. mentagrophytes, or antiviral activities against HIV entry at 20 µg/mL (62.9-66.7) µM. Compounds 1 and 3 did not show antiviral activities against Ebola entry at 20 µg/mL either; only 2 was found to show an 81% inhibitory effect against Ebola entry activity at 20 µg/mL (66.7 µM). The bioactivity evidence suggested that this type of compound could be a valuable antiviral lead for further structure modification to improve the antiviral potential.

Mechanistic Pathways and Molecular Targets of Plant-Derived Anticancer ent-Kaurane Diterpenes.

Since the first discovery in 1961, more than 1300 ent-kaurane diterpenoids have been isolated and identified from different plant sources, mainly the genus Isodon. Chemically, they consist of a perhydrophenanthrene subunit and a cyclopentane ring. A large number of reports describe the anticancer potential and mechanism of action of ent-kaurane compounds in a series of cancer cell lines. Oridonin is one of the prime anticancer ent-kaurane diterpenoids that is currently in a phase-I clinical trial in China. In this review, we have extensively summarized the anticancer activities of ent-kaurane diterpenoids according to their plant sources, mechanistic pathways, and biological targets. Literature analysis found that anticancer effect of ent-kauranes are mainly mediated through regulation of apoptosis, cell cycle arrest, autophagy, and metastasis. Induction of apoptosis is associated with modulation of BCL-2, BAX, PARP, cytochrome c, and cleaved caspase-3, -8, and -9, while cell cycle arrest is controlled by cyclin D1, c-Myc, p21, p53, and CDK-2 and -4. The most common metastatic target proteins of ent-kauranes are MMP-2, MMP-9, VEGF, and VEGFR whereas LC-II and mTOR are key regulators to induce autophagy.

1α,2α-Epoxy-3ß-hydroxy oleanolic acid derivatives regulation of the metabolism, haemolysis and ß-lactamase gene expression in vitro and their structure-microbicidal activity relationship.

Oleanolic acid (OA), one of the major pentacyclic triterpenes abundantly present in nature, is a promising compound with various biological activities, including anti-inflammatory, anti-ulcer, hepatoprotective, antidiabetic, fungicidal and antiparasitic properties. Therefore, a series of derivatives of 1α,2α-epoxy-3ß-hydroxyl oleanolic acid derivatives were designed and synthesized, and their antibacterial activities were investigated in vitro. Based on these results, the compounds with antibacterial activity were screened by RT-PCR to determine whether they can regulate the expression of genes related to metabolism, haemolysis, and ß-lactamase in vitro, and the structure-microbicidal activity relationship of each compound was analyzed. Our study shows that some of the modifications in the synthetic compounds, such as the introduction of an ortho-cyano-substituted benzyl group and a short chain alkyl ester at the 28-carboxyl, as well as the introduction of an acetyl group at the 3-hydroxyl group of ring A, could enhance antibacterial activity. This provides basic evidence for the optimization of 1α,2α-epoxy-3ß-hydroxyl oleanolic acid derivatives. The antibacterial mechanism of the active OA derivatives appears to involve the regulation of expression of metabolism-associated genes in Escherichia coli, haemolysis-associated genes in Bacillus subtilis, metabolism-related genes in Klebsiella pneumonia and ß-lactamase-associated genes in Acinetobacter baumannii. Some OA derivatives were bactericidal to three of the strains and appeared to regulate gene expression associated with metabolism, haemolysis, and ß-lactamase in vitro. These newly designed OA derivatives possess unique antibacterial activities and may be potentially useful for prophylactic or therapeutic intervention of bacterial infections.