In vitro and in silico studies reveal antidiabetic properties of arylbenzofurans from the root bark of Morus mesozygia Stapf.

Diabetes remains an important disease worldwide with about 500 million patients globally. In tropical Africa, Morus mesozygia is traditionally used in the treatment of diabetes. Biological and phytochemical investigation of the root bark extracts of the plant led to the isolation of a new prenylated arylbenzofuran named 7-(3-hydroxy-3-methylbutyl)moracin M (1) and two congeners, moracins P (2) and M (3). When compared to acarbose (IC50 = 486 µM), all the isolated compounds are better inhibitors of α-glucosidase with in vitro IC50 values of 16.9, 16.6, and 40.9 µM, respectively. However, they were not active against α-amylase. The compounds also demonstrated moderate inhibition of dipeptidyl peptidase-4 (DPP4). Based on in silico docking studies, all isolates (1, 2, and 3) exhibit binding affinities of -8.7, -9.5, and -8.5 kcal/mol, respectively against α-glucosidase enzyme (PDB: 3AJ7). They are stabilized within the α-glucosidase active site through hydrogen bonds, pi interactions, and hydrophobic interactions. This study provides scientific support for the traditional use of Morus mesozygia in the treatment of diabetes as well as adding to the repository of α-glucosidase inhibitory agents.

Prenylated Isoflavanones with Antimicrobial Potential from the Root Bark of Dalbergia melanoxylon.

Dalbergia melanoxylon Guill. & Perr (Fabaceae) is widely utilized in the traditional medicine of East Africa, showing effects against a variety of ailments including microbial infections. Phytochemical investigation of the root bark led to the isolation of six previously undescribed prenylated isoflavanones together with eight known secondary metabolites comprising isoflavanoids, neoflavones and an alkyl hydroxylcinnamate. Structures were elucidated based on HR-ESI-MS, 1- and 2-D NMR and ECD spectra. The crude extract and the isolated compounds of D. melanoxylon were tested for their antibacterial, antifungal, anthelmintic and cytotoxic properties, applying established model organisms non-pathogenic to humans. The crude extract exhibited significant antibacterial activity against Gram-positive Bacillus subtilis (97% inhibition at 50 µg/mL) and antifungal activity against the phytopathogens Phytophthora infestans, Botrytis cinerea and Septoria tritici (96, 89 and 73% at 125 µg/mL, respectively). Among the pure compounds tested, kenusanone H and (3R)-tomentosanol B exhibited, in a panel of partially human pathogenic bacteria and fungi, promising antibacterial activity against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and Mycobacterium showing MIC values between 0.8 and 6.2 µg/mL. The observed biological effects support the traditional use of D. melanoxylon and warrant detailed investigations of its prenylated isoflavanones as antibacterial lead compounds.

Flavanols from Tetrapleura tetraptera with cytotoxic activities.

Tetrapleura tetraptera is a medicinal plant used in East and West Africa to treat inflammation and related diseases. From the stem bark of the plant, three previously undescribed flavan-3-ol derivatives named (2R,3S)-3,3',5',7-tetrahydroxy-4'-methoxyflavane (1), (2R,3S)-3',5',7-trihydroxy-4'-methoxyflavane-3-O-ß-D-glucopyranoside (2), and (2R,3S,4S)-3,3',4,5',7-pentahydroxy-4'-methoxyflavane (3) were isolated with three known analogues. The structural elucidation of the compounds was performed based on NMR spectroscopy and HRMS data analyses. The absolute configurations around the stereogenic carbons were determined using Circular Dichroism (ECD) and density functional theory (DFT) calculations. The cytotoxicity of the isolated compounds was tested using resazurin reduction assay. Compound 1 was moderately active against both recalcitrant leukemia cell lines with IC50 values of 21.90 µM towards CCRF-CEM and 50.80 towards CEM/ADR5000. Similar level of activity was observed for compound 3 against CCRF-CEM cell line, IC50 = 35.50 µM. All the tested compounds were not cytotoxic compared with the standard drug, doxorubicin, with IC50 values of 0.0075 against CCRF-CEM and 24.30 µM against CEM/ADR5000.

Antibacterial secondary metabolites from Vernonia auriculifera Hiern (Asteraceae) against MDR phenotypes.

Purification of the aerial parts of Vernonia auriculifera Hiern afforded steroids (1-2), flavonoids (3-5), and polyalcohol (6). Their structures were determined using spectral evidences as well as by comparison with reported data. Iodonitrotetrazolium chloride (INT) colorimetric assay was used to assess the antibacterial activity of the extract and isolates against 13 pathogenic strains. The crude extract showed strong antibacterial activity (MIC < 100 µg/mL) against the tested bacterial strains. When combined with an efflux pump inhibitor phenylalanine beta naphthylamide (PAßN), the inhibition potency of the extract was substantially enhanced with the lowest MIC value at 4 µg/mL. Compounds 5 and 6 showed moderate activity (MIC < 100 µg/mL) against 12/13 (92.3%), and 8/13 (61.5%) bacterial strains, respectively. A minimal bactericidal concentration (MBC)/minimal inhibitory concentration (MIC) ratio ≤ 4 indicated their bactericidal effect against Escherichia coli, Enterbacter aerogenes, Klebsiella pneumoniae, Providencia stuartii, Pseudomonas aeruginosa, and Staphylococcus aureus.

Mechanism of Action of Endophytic Fungi Hypocrea lixii and Beauveria bassiana in Phaseolus vulgaris as Biopesticides against Pea Leafminer and Fall Armyworm.

Endophytic fungal isolates Hypocrea lixii F3ST1 and Beauveria bassiana G1LU3 were evaluated for their potential to endophytically colonize and induce active compounds in Phaseolus vulgaris, as a defense mechanism against pea leafminer (Liriomyza huidobrensis) and fall armyworm (Spodoptera frugiperda). Endophytic colonization was achieved through seed inoculation with the volatile emissions from P. vulgaris plants being analyzed using GC-MS. The crude extracts of P. vulgaris obtained using methanol and dichloromethane were assayed against leafminer and fall armyworm larvae using leaf dipping and topical application, respectively. The two isolates successfully colonized the entire host plant (roots, stems, and leaves) with significant variation (p < 0.001) between fungal isolates and the controls. The results showed qualitative differences in the volatile profiles between the control plants, endophytically colonized and insect-damaged plants attributed to fungal inoculation and leafminer damage. The crude methanol extracts significantly reduced the percentage pupation of 2nd instar leafminer larvae (p < 0.001) and adult-flies emergence (p < 0.05). The survival of the 1st instar fall armyworm larvae was also significantly reduced (p < 0.001) compared to the controls. This study demonstrated the high potential of endophytic fungi H. lixii and B. bassiana in inducing mainly specific defense compounds in the common bean P. vulgaris that can be used against pea leafminer and fall armyworm.

Inhibition of Proinflammatory Cytokine Release by Flavones and Flavanones from the Leaves of Dracaena steudneri Engl.

The leaves of Dracaena steudneri yielded 6 new flavonoids-3,5,7-trihydroxy-6-methyl-3',4'-methylenedioxyflavone (1: ), 5,7-dihydroxy-3-methoxy-6-methyl-3',4'-methylenedioxyflavone (2: ), 3,5,7-trihydroxy-6-methoxy-3',4'-methylenedioxyflavone (3: ), (2S,3S)-3,7-dihydroxy-6-methoxy-3',4'-methylenedioxyflavanone (4: ), 4',5,7-trihydroxy-3,3',8-trimethoxy-6-methylflavone (5: ), (2R) 7-hydroxy-2',8-dimethoxyflavanone (6: )-together with 13 known congeners. Their structures were established using spectroscopic and spectrometric methods including NMR, CD, and HRMSn measurements. The compounds were evaluated for their anti-inflammatory potential through measurement of the levels of cytokines IL-1ß, IL-2, GM-CSF, and TNF-α in the supernatant of human peripheral blood mononuclear cells stimulated by lipopolysaccharide. Flavones derivatives 1: -4: with a C-3'/4' methylenedioxy substituent led to a substantial increase in the production of IL-1ß and GM-CSF out of 4 pro-inflammatory cytokines relative to LPS control. Quercetin derivatives 5, 11,: and 13: with a hydroxyl group at C-4' inhibited the production of IL-2, GM-CSF, and TNF-α. The presence of a C-2/C-3 double bond in 14: was pivotal to the significantly stronger (0.4 to 27.5% of LPS control) inhibitory effect compared to its dihydro derivative 8: (36.2 to 262.7% of LPS control) against all tested cytokines. It is important to note that the inhibitory activity of 14: was substantially higher than that of the standard drug used, ibuprofen.

Anti-inflammatory steroidal sapogenins and a conjugated chalcone-stilbene from Dracaena usambarensis Engl.

Four new steroidal sapogenins, dracaenogenins CF (1-4), a new conjugated chalcone-stilbene, 3''-methoxycochinchinenene H (5) together with eight known compounds namely, (25S)-spirosta-1,4-dien-3-one (6), trans-resveratrol (7), 4,4'-dihydroxy-3'-methoxychalcone (8), N-trans-coumaroyltyramine (9), N-trans-p-coumaroyloctopamine (10), N-trans-feruloyloctopamine (11), 7-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-N2,N3-bis(4-hydroxyphenethyl)-6-methoxy-1,2-dihydronaphthalene-2,3-dicarboxamide (12) and grossamide (13) were isolated from the stems of Dracaena usambarensis Engl. from Kenya. It is important to note that compounds 12 and 13 are being reported from this genus for the first time. Structural elucidation of the isolated compounds was done using spectroscopic (NMR, UV, IR, optical rotation) and spectrometric (HRESIMS) techniques. The absolute and relative configurations of the isolated compounds were determined by employing single crystal X-ray crystallography analysis, NOESY correlations and coupling constants. The anti-inflammatory potencies of the isolated compounds were evaluated by measuring the levels of four cytokines (IL-1ß, IL-2, GM-CSF and TNF-α) in the supernatant media of human peripheral blood mononuclear cells (PBMCs) stimulated by lipopolysaccharide (LPS). At the tested concentration of 100 µM, the new conjugated chalcone-stilbene 5, the dihydrochalcone, 8 and the lignanamide, 13 were substantially more potent than the standard drug, ibuprofen, inhibiting the release of all the cytokines, IL-1ß, IL-2, GM-CSF and TNF-α from 0.06-58.04% compared to LPS control. These compounds should therefore be considered for development into anti-inflammatory drug candidates. Compound 7 significantly decreased the release of GM-CSF (6.11% of LPS control) and TNF-α (18.35% of LPS control). The cytokine TNF-α was sensitive to all the tested compounds 1-13.

Anti-inflammatory norhopanes from the root bark of Fagaropsis angolensis (Engl.) H.M.Gardner.

Two new norhopane derivatives namely 3ß,6ß,22-trihydroxy-7ß,11α-di[(4-hydroxybenzoyl)oxy]-21αH-24-norhopa-4(23)-ene (1) and 3ß,6ß,22-trihydroxy-7ß-[(4-hydroxybenzoyl)oxy]-21αH-24-norhopa-4(23)-ene (2) together with two previously reported compounds, including a norhopane, 3ß,6ß,11α-trihydroxy-7ß-[(4-hydroxybenzoyl)oxy]-24-norhopa-4(23),17(21)-diene (3) and a norneohopane, (21αH)-24-norneohopa-4(23), 22(29)-diene-3ß,6ß,7ß-triol 7-caffeate (4) were isolated from the root bark of Fagaropsis angolensis. Elucidation of their structures was achieved by spectroscopic (NMR, IR and UV) and spectrometric (HRESIMS) data and by comparison of these data with those of related compounds in the literature. Compounds 1-4 were evaluated for their anti-inflammatory activity by measuring the levels of cytokines, IL-1ß, IL-2, GM-CSF and TNF-α in lipopolysaccharide (LPS) stimulated peripheral blood mononuclear cells (PBMC). All tested compounds decreased secretion of IL-1ß and TNF-α. Compounds 2 and 4 caused significant decrease of the production of IL-2, GM-CSF and TNF-α compared to the reference drug, ibuprofen. These findings showed that the root barks of F. angolensis are rich source of norhopane derivatives and further provide a scientific rationale of using this plant in Kenyan folk medicine to relieve pain.