Antimicrobial activity of anthraquinone compounds of emodine type has been reported by many authors. These compounds are found in Vismia laurentii (Clusiaceae), a plant used in traditional pharmacopoeia for treatment of microbial infections among others affections. The continuous identification of new compounds has raised the problem of the relation between the structure and antimicrobial properties. The yeast growth kinetics parameters were not influenced by the pH variation as it was the case for the other tested bacteria. Fungicidal activities were noted for all molecules while only few of them had bactericidal activities, mostly on Gram positive bacteria. Mathematical model establishing a quantitative relationship between physicochemical properties of molecules and their fungicidal activities were obtained for Candida albicans and showed that physicochemical properties impacting on antifungal activity were polarizability, partition coefficient, molecular weight and hydrogen bond acceptor. This work demonstrated that the presence of a long aliphatic chain methoxy group substituted in position two of the emodine structure increased the antibacterial properties of the studied compounds. Moreover this antimicrobial property depends on the pH of the environment, and specifically on the polarizability and number of hydrogen bond acceptors of the compound.

Limonoids are highly oxygenated compounds with a prototypical structure. Their occurrence in the plant kingdom is mainly confined to plant families of Meliaceae and Rutaceae. Owing to their wide range of pharmacological and therapeutic properties, this study was aimed at investigating the potential nitric oxide (NO) and acetylcholinesterase (AChE) inhibitory activity and the cytotoxicity of three limonoids: trichilia lactone D5 (1), rohituka 3 (2) and dregeanin DM4 (3), isolated from Trichilia welwitschii C.DC. Results indicated that the three limonoids had low cytotoxicity towards Vero cells with LC50 values ranging from 89.17 to 75.82 μg/mL. Compounds (2) and (3) had lower cytotoxicity compared to puromycin and doxorubicin used as reference cytotoxic compounds. Compound (1) (LC50 of 23.55 μg/mL) had good antiproliferative activity against RAW 264.7 cancer cells. At the lowest concentration tested (0.5 µg/mL), compound (2) and (3) released the lowest amount of nitric oxide (2.97 and 2.93 µM, respectively). The three limonoids had anti-AChE activity with IC50 values ranged of 19.13 μg/mL for (1), 34.15 μg/mL for (2) and 45.66 μg/mL for (3), compared to galantamine (IC50 of 8.22 μg/mL) used as positive control. The limonoid compounds studied in this work inhibited nitric oxide production in LPS-stimulated macrophages and had anti-AChE activity. Trichilia lactone D5 had potential antiproliferative activity against RAW 264.7 cancer cells. The limonoids had low cytotoxicity towards Vero cells lines. This study provided further examples of the importance of limonoids compounds as potential AChE inhibitors and anti-inflammatory agents targeting the inhibition of NO production.

Bioassay-guided fractionation of the stem bark of Symphonia globulifera has yielded three known xanthones, ugaxanthone (1), mbarraxanthone (2) and gentisein (3), two biflavonoid derivatives named GB2 (4) and manniflavanone GB3 (5), and one new polyoxygenated xanthone with an isoprenoid group, named globulixanthone F (6). The structures of these compounds were elucidated by means of spectroscopic methods. The spectral data of 1 and 2 are reported here for the first time, as well as the antimicrobial activity of globulixanthone F against a range of microorganisms. We also report the total synthesis of the xanthone skeleton.

Three new lupan-type triterpernoid derivatives, namely globimetulin A (1), B (2) and C (3), were isolated from the shoot of Globimetula dinklagei (Loranthaceae), a hemiparasitic plant growing on Manihot esculenta, along with five known compounds: friedelin (4), friedelan-3-ol (5), 28-hydroxyfriedelin (6), 4-hydroxy-3,5-dimethoxybenzoic acid (7) and (1R,5S,7S)-7-[2-(4-hydroxyphenyl)ethyl]-2,6-dioxabicyclo[3.3.1]nonan-3-one (8). The structures of the new compounds were elucidated by detailed analyses of their MS, IR, 1D and 2D NMR spectral data and chemical evidence. Some of these compounds were evaluated in vitro for their antimicrobial activities against a wide range of microorganisms, but none of them exhibited noticeable activity.