Laevifins A-G, clerodane diterpenoids from the Bark of Croton oblongus Burm.f

Cytotoxic ent-abietane diterpenoids from the leaves of Croton lachnocarpus Benth

A phytochemical investigation on the 90% ethanol extract of the leaves of Croton lachnocarpus Benth. led to three new ent-abietane diterpenoids, 7β,15-dihydroxy-ent-abieta-8,11,13-trien-3-one (1), 2β,15-dihydroxy-ent-abieta-8,11,13-triene (2), and 7β,13α,15-trihydroxy-ent-abieta-8(14)-en-3-one (3). Structural elucidation of all the compounds were performed by spectral methods such as 1 D and 2 D (¹H-¹H COSY, HMQC, NOESY and HMBC) NMR spectroscopy, in addition to electronic circular dichroism (ECD) spectra. The isolated compounds were tested in vitro for cytotoxic activity against 6 tumor cell lines. As a result, compound 3 exhibited some cytotoxicities against all the tested tumor cell lines with IC₅₀ value less than 30 μM.

Antimicrobial ent-abietane diterpenoids from the leaves of Croton cascarilloide

Three new ent-abietane diterpenoids, 6β-hydroxy-ent-abieta-7,13-dien-3-one (1), 2β,13α,15-trihydroxy-ent-abieta-8(14)-en-3-one (2), and 2β,9α,13β,15-tetrahydroxy-ent-abieta-7-en-3-one (3), were isolated from 90% ethanol extract of the leaves of Croton cascarilloide. Their structures were determined by spectral methods such as 1D and 2D (¹H-¹H COSY, HMQC, NOESY, and HMBC) NMR spectroscopy, in addition to electronic circular dichroism (ECD) spectra. The isolated diterpenoids were tested in vitro for antimicrobial activity against 6 pathogenic microorganisms. As a result, compounds 1-3 exhibited antimicrobial activity against the tested Gram positive bacteria with minimum inhibitory concentration values less than 50 μg/ml.

ent-Clerodane diterpenoids from the stems of Croton krabas

The first phytochemical investigation from the stems of Croton krabas resulted in the isolation of three new ent-clerodane diterpenoids, crotonkrabases A-C (1-3), along with two known compounds, 12-oxohardwickiic acid (4) and crotonpyrone B (5). Their structures were elucidated using extensive spectroscopic methods. The structure of 3 was unambiguously proven by X-ray crystallography. Furthermore, the absolute configurations of compounds 1-3 were identified by NOESY and the comparison of their experimental ECD spectra with those of calculated ECD spectra reported in the literature. Compounds 1, 2, and 5 showed antibacterial activities against two Gram-positive bacteria (Bacillus cereus and Bacillus subtilis); whereas compound 4 exhibited weak antibacterial against B. cereus. In addition, compound 4 showed potent α-glucosidase inhibitory activity, which was lower than the reference standard acarbose.

Catalytic Hydroxycyclopropanol Ring-Opening Carbonylative Lactonization to Fused Bicyclic Lactones

A novel palladium-catalyzed ring opening carbonylative lactonization of readily available hydroxycyclopropanols was developed to efficiently synthesize tetrahydrofuran (THF) or tetrahydropyran (THP)-fused bicyclic γ-lactones, two privileged scaffolds often found in natural products. The reaction features mild reaction conditions, good functional group tolerability, and scalability. Its application was demonstrated in a short total synthesis of (±)-paeonilide. The fused bicyclic γ-lactone products can be easily diversified to other medicinally important scaffolds, which further broadens the application of this new carbonylation method.

The Antiangiogenic Activity of Naturally Occurring and Synthetic Homoisoflavonoids from the Hyacinthaceae ( sensu APGII)

Excessive blood vessel formation in the eye is implicated in wet age-related macular degeneration, proliferative diabetic retinopathy, neovascular glaucoma, and retinopathy of prematurity, which are major causes of blindness. Small molecule antiangiogenic drugs are strongly needed to supplement existing biologics. Homoisoflavonoids have been previously shown to have potent antiproliferative activities in endothelial cells over other cell types. Moreover, they demonstrated a strong antiangiogenic potential in vitro and in vivo in animal models of ocular neovascularization. Here, we tested the antiangiogenic activity of a group of naturally occurring homoisoflavonoids isolated from the family Hyacinthaceae and related synthetic compounds, chosen for synthesis based on structure-activity relationship observations. Several compounds showed interesting antiproliferative and antiangiogenic activities in vitro on retinal microvascular endothelial cells, a disease-relevant cell type, with the synthetic chromane, 46, showing the best activity (GI50 of 2.3 × 10-4 μM).