Evaluation of cholinesterase inhibitory activity and cytotoxicity of synthetic derivatives of di- and triterpene metabolites from Pinus silvestris and Dipterocarpus alatus resins

New Dipterocarpol-Based Molecules with α-Glucosidase Inhibitory and Hypoglycemic Activity

Dammarane triterpenoids are affordable and bioactive natural metabolites with great structural potential, which makes them attractive sources for drug development. The aim of the study was to investigate the potency of new dipterocarpol derivatives for the treatment of diabetes. Two dammaranes (dipterocarpol and its 20(24)-diene derivative) were modified by a Claisen-Schmidt aldol condensation to afford C2(E)-arylidenes in good yields. The majority of the synthesized compounds exhibited an excellent-to-moderate inhibitory effect toward α-glucosidase (from S. saccharomyces), among them eight compounds showed IC50 values less than 10 μM. 3-Oxo-dammarane-2(E)-benzylidenes (holding p-hydroxy- 3 l and p-carbonyl- 3 m substituents) demonstrated the most potent α-glucosidase inhibition with IC50 0.753 and 0.204 μM, being 232- and 857-times more active than acarbose (IC50 174.90 μM), and a high level of NO inhibition in Raw 264.7 cells with IC50 of 1.75 and 4.57 μM, respectively. An in vivo testing of compound 3 m (in a dose of 20 mg/kg) on a model of streptozotocin-induced T1DM in rats showed a pronounced hypoglycemic activity, the ability to reduce effectively the processes of lipid peroxidation in liver tissue and decrease the excretion of glucose and pyruvic acid in the urine. Compound 3 m reduced the death of diabetic rats and preserved their motor activity.

Inhibitory properties of quinopimaric acid derivatives towards cholinesterases

A series of new diterpene quinopimaric acid derivatives modified at the hydroxyl group with different pharmacophore fragments has been synthesised and their (along with previously obtained compounds) inhibitory properties towards cholinesterases were studied. Thereby an indole-3-acetyl derivative 7 and a propargyl substituted compound 28 were shown to be excellent and acetylcholinesterase-selective inhibitors. Both compounds inhibited the enzyme as a mixed type inhibitor, and Ki values of 0.41 and 0.44 µM and Ki' values of 0.98 and 2.26 µM were determined. The binding interactions between all active compounds and ligands protein were confirmed through molecular docking study.

Isoxazole/Isoxazoline Skeleton in the Structural Modification of Natural Products: A Review

Isoxazoles and isoxazolines are five-membered heterocyclic molecules containing nitrogen and oxygen. Isoxazole and isoxazoline are the most popular heterocyclic compounds for developing novel drug candidates. Over 80 molecules with a broad range of bioactivities, including antitumor, antibacterial, anti-inflammatory, antidiabetic, cardiovascular, and other activities, were reviewed. A review of recent studies on the use of isoxazoles and isoxazolines moiety derivative activities for natural products is presented here, focusing on the parameters that affect the bioactivity of these compounds.

Synthetic modifications of abietane diterpene acids to potent antimicrobial agents

Among abietane type semisynthetic diterpenoids, a series of quinopimaric and maleopimaric acid derivatives modified at the carboxyl and carbonyl groups, and in ring E were synthesised to obtain new compounds with antimicrobial potency against Mycobacterium tuberculosis H₃₇Rv and key ESKAPE pathogens. It was found that compound 8 exhibited low toxicity to human embryonic kidney cell line HEK-293 (> 32 μg/mL) and showed significant bacteriostatic activity against methicillin-resistant Staphylococcus aureus (MRSA) (MIC ≤ 0.25 µg/mL) and excellent antifungal activity against Cryptococcus neoformans var. grubii (MICs ≤0.25 µg/mL) being ≈4 and ≈30 fold more active than vancomycin and fluconazole. It also showed moderate activity against fungus Candida albicans (MIC ≤ 0.25 µg/mL). Compound 9 inhibited M. tuberculosis H₃₇Rv with MIC of 1.25 µg/mL. The docking studies suggest possible interactions of the leading compounds with the molecular targets.