Antibacterial and cytotoxic prenylated dihydrochalcones from Eriosema montanum

Fungal Prenyltransferase AnaPT and Its F265 Mutants Catalyze the Dimethylallylation at the Nonaromatic Carbon of Phloretin

Phloretin is widely found in fruit and shows various biological activities. Here, we demonstrate the dimethylallylation, geranylation, and farnesylation, particularly the first dimethylallylation at the nonaromatic carbon of phloretin (1) by the fungal prenyltransferase AnaPT and its mutants. F265 was identified as a key amino acid residue related to dimethylallylation at the nonaromatic carbon of phloretin. Mutants AnaPT_F265D, AnaPT_F265G, AnaPT_F265P, AnaPT_F265C, and AnaPT_F265Y were discovered to generally increase prenylation activity toward 1. AnaPT_F265G catalyzes the O-geranylation selectively at the C-2' hydroxyl group, which involves an intramolecular hydrogen bond with the carbonyl group of 1. Seven products, 1D5, 1D7-1D9, 1G2, 1G4, and 1F2, have not been reported prior to this study. Twelve compounds, 1D3-1D9, 1G1-1G3, and 1F1-1F2, exhibited potential inhibitory effects on α-glucosidase with IC50 values ranging from 11.45 ± 0.87 to 193.80 ± 6.52 μg/mL. Among them, 1G1 with an IC50 value of 11.45 ± 0.87 μg/mL was the most potential α-glucosidase inhibitor, which is about 30 times stronger than the positive control acarbose with an IC50 value of 346.63 ± 15.65 μg/mL.

Cytotoxic potential of dihydrochalcones from Eriosema glomeratum and their semi-synthetic derivatives

In the search of cytotoxic dihydrochalcones, this investigation led to the isolation of seven compounds (1-7) from Eriosema glomeratum and the preparation of eight derivatives (8-15). The cytotoxicity of samples was evaluated against lung (A549), breast (MCF-7), and cervical (HeLa) human cancer cells. The CH2Cl2/MeOH extract of the aerial part had strong cytotoxicity against all cells [IC50 11.2 (MCF-7), 8.4 (HeLa) and 13.1 (A549) μg/mL]. A strong activity was also displayed by the n-hexane fraction on MCF-7 (IC50 11.2 μg/mL). The precursor 3 and the derivative 8 were specifically found as strong cytotoxic agents toward MCF-7 (7.6 μM) and HeLa (3.1 μM), respectively and were more effective than the positive control. Derivatives 8 (3.1 μM) and 9 (21.3 μM) against HeLa were most potent than their precursor 3 (23.7 μM). This is the first preparation of 8-14 as well as the cytotoxicity of 3, 4, 8-15, fractions, and extract.

Benzo[b]naphtho[2,1-d]furans and 2-Phenylnaphthalenes from Streblus usambarensis

Three new benzo[b]naphtho[2,1-d]furans, usambarins A-C (1-3), five new 2-phenylnaphthalenes, usambarins D-H (4-8), a new flavan (9), and a new phenyl-1-benzoxepin (10) as well as two known compounds (11 and 12) were isolated from the extract of the stem and roots of Streblus usambarensis (Moraceae). The structures were deduced using NMR spectroscopic and mass spectrometric analyses, and those of compounds 1 and 4 were confirmed by X-ray crystallography. Usambarin D (4) demonstrated moderate antibacterial activity (MIC 9.0 μM) against Bacillus subtilis, while none of the tested compounds were effective against Escherichia coli.

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.

In Vitro Antiplasmodial and Cytotoxic Activities of Compounds from the Roots of Eriosema montanum Baker f. (Fabaceae)

Malaria remains one of the leading causes of death in sub-Saharan Africa, ranked in the top three infectious diseases in the world. Plants of the Eriosema genus have been reported to be used for the treatment of this disease, but scientific evidence is still missing for some of them. In the present study, the in vitro antiplasmodial activity of the crude extract and compounds from Eriosema montanum Baker f. roots were tested against the 3D7 strain of Plasmodium falciparum and revealed using the SYBR Green, a DNA intercalating compound. The cytotoxicity effect of the compounds on a human cancer cell line (THP-1) was assessed to determine their selectivity index. It was found that the crude extract of the plant displayed a significant antiplasmodial activity with an IC₅₀ (µg/mL) = 17.68 ± 4.030 and a cytotoxic activity with a CC₅₀ (µg/mL) = 101.5 ± 12.6, corresponding to a selective antiplasmodial activity of 5.7. Bioactivity-guided isolation of the major compounds of the roots' crude extract afforded seven compounds, including genistein, genistin and eucomic acid. Under our experimental conditions, using Artemisinin as a positive control, eucomic acid showed the best inhibitory activity against the P. falciparum 3D7, a well-known chloroquine-sensitive strain. The present results provide a referential basis to support the traditional use of Eriosema species in the treatment of malaria.