DICHLOROMETHANE EXTRACT OF THE LEAVES OF ARBUTUS PAVARII PAMP. EXHIBITS CYTOTOXICITY AGAINST THE PROSTATE CANCER CELL LINE PC3: A BIOASSAY-GUIDED ISOLATION AND IDENTIFICATION OF ARBUTIN AND BETULINIC ACID METHYL ESTER

Background: Arbutus pavarii Pamp. (fam. Ericaceae), commonly known as “Shmeri”, “Shmar” and “Libyan Strawberry”, is an endemic Libyan medicinal plant, growing almost exclusively in the Al-Jabel Al-Akhdar mountainous region in Libya. Aims: To assess the cytotoxicity of A. pavarii against human cancer cell lines and to carry out bioassay-guided isolation and identification of compounds. Materials and Methods: Shed-dried and ground leaves of A. pavarii were Soxhlet-extracted, successively, with n-hexane, dichloromethane (DCM) and methanol (MeOH), and assessed for cytotoxicity against several human cancer cell lines using the MTT assay. The cytotoxicity of the DCM extract against the normal human prostate cell line PNT2 was also assessed to determine the selectivity index (SI). The DCM extract was subjected to vacuum liquid chromatography (VLC) to produce eight fractions. A reversed-phase preparative HPLC analysis of the active VLC fraction was carried out to purify the major compounds present in the active fraction, and the structures of the compounds were elucidated by spectroscopic means. Results: The DCM extract was more cytotoxic against the PC3 cell line (IC50= 26 mg/mL) but less to the normal human prostate cell line PNT2 (IC50 = 90 mg/mL) with a selectivity index of 3.5. VLC analysis produced 8 fractions, with fraction VLC-5 most active against PC3 cells. Prep-HPLC-based purification of VLC-5 afforded the isolation of arbutin (1) and betulinic acid methyl ester (2), the structures of which were elucidated by spectroscopic means. Conclusion: The DCM extract of the leaves of A. pavarii exhibited significant cytotoxicity to PC3 cells, but much less cytotoxicity against normal human prostate cell line. The isolated compounds from the active fraction, arbutin (1) and betulinic acid methyl ester (2), which were previously shown to possess cytotoxic properties, could be responsible for the cytotoxicity of the DCM extract

RESEARCH ACTIVITIES IN THE CENTRE FOR NATURAL PRODUCTS DISCOVERY IN 2023

In 2023, the Centre for Natural Products Discovery (CNPD) made significant strides in the scientific community through a series of impactful research initiatives. These efforts underscore our commitment to harnessing the world’s natural resources to advance health. The fertile research environment at the CNPD has given rise to various sections, each contributing innovative and practical applications. Our goal here is to provide a concise overview of our research activities for the year. While this summary is not exhaustive, it focuses on the work of our section leaders, which in turn encompasses the contributions of numerous other researchers both within and outside the CNPD

Anti-MRSA Activity of Oxysporone and Xylitol from the Endophytic Fungus Pestalotia sp. Growing on the Sundarbans Mangrove Plant Heritiera fomes

Heritiera fomes Buch.-Ham., a mangrove plant from the Sundarbans, has adapted to a unique habitat, muddy saline water, anaerobic soil, brackish tidal activities and high microbial competition. Endophytic fungal association protects this plant from adverse environmental conditions. This plant is used in Bangladeshi folk medicine, but it has not been extensively studied phytochemically, and there is hardly any report on investigation on endophytic fungi growing on this plant. In this study, endophytic fungi were isolated from the surface sterilized cladodes and leaves of H. fomes. The antimicrobial activities were evaluated against two Gram-positive and two Gram-negative bacteria and the fungal strain, Candida albicans. Extracts of Pestalotia sp. showed activities against all test bacterial strains, except that the EtOAc extract was inactive against E. coli. The structures of the purified compounds, oxysporone and xylitol, were elucidated by spectroscopic means. The anti-MRSA potential of the isolated compounds were determined against various MRSA strains, i.e., ATCC 25923, SA-1199B, RN4220, XU212, EMRSA-15 and EMRSA-16, with MIC values ranging from 32-128 g/mL. This paper, for the first time, reports on the anti-MRSA property of oxysporone and xylitol, isolation of the endophyte Pestalotia sp. from H. fomes, and isolation of xylitol from a Pestalotia sp

Cytotoxicity of Libyan Juniperus phoenicea against Human Cancer Cell Lines A549, EJ138, Hepg2 and MCF7

Background: The current study was undertaken to assess the cytotoxicity of the leaves of Libyan Juniperus phoenicea (Cupressaceae) against human cancer cell lines. Methods: The cytotoxicity of the n-hexane, dichloromethane (DCM) and methanol (MeOH) extracts of the leaves of J. phoenicea (JP), obtained from sequential Soxhlet extractions, was assessed against four human cancer cell lines: EJ138 (human bladder carcinoma), HepG2 (human liver hepatocellular carcinoma), A549 (human lung carcinoma) and MCF7 (human breast adenocarcinoma) using the MTT assay. Results: The cell line A549 was the most sensitive to the JP extracts, with the highest level of cytotoxicity with the IC50 values of 16, 13 and 100 µg/mL for the DCM, n-hexane and MeOH extracts, respectively. However, generally the most potent cytotoxic extract across the other cells tested was the n-hexane extract, followed by the DCM extract, whilst the MeOH extracts showed little or no cytotoxicity. The percentage of viability of cells decreased as the concentration of test compounds increased. The cytotoxicity of various chromatographic fractions from the extracts was also studied against the A459 cells. For the n-hexane fractions, the IC50 values were 160, 62, 90, 30, 9.5 and 40 µg/mL for fractions 1 to 5 and 7, respectively. Fractions 4 and 5 showed the greatest effect. DCM fractions 2, 3 and 4 had the IC50 values of 60, 92 and 19 µg/mL, respectively, and DCM fractions 5 to 8 were non-cytotoxic. Fractions 1 and 2 of the MeOH extract were non-cytotoxic, whereas cytotoxicity was observed for fractions 3 and 4 with IC50 values of 50 and 85 µg/mL, respectively. Conclusion: The outcome of the present study suggested that the JP leaves possess cytotoxic activities. The high level of cytotoxicity of the n-hexane and DCM extracts suggested that lipophilicity might affect the cytotoxicity of JP, where the less polar compounds had the strongest cytotoxicity

Exposure to Anacardiaceae Volatile Oils and Their Constituents Induces Lipid Peroxidation within Food-Borne Bacteria Cells

The chemical composition of the volatile oils from five Anacardiaceae species and their activities against Gram positive and negative bacteria were assessed. The peroxidative damage within bacterial cell membranes was determined through the breakdown product malondialdehyde (MDA). The major constituents in Anacardium humile leaves oil were (E)-caryophyllene (31.0%) and α-pinene (22.0%), and in Anacardium occidentale oil they were (E)-caryophyllene (15.4%) and germacrene-D (11.5%). Volatile oil from Astronium fraxinifolium leaves were dominated by (E)-β-ocimene (44.1%) and α-terpinolene (15.2%), whilst the oil from Myracrodruon urundeuva contained an abundance of δ-3-carene (78.8%). However, Schinus terebinthifolius leaves oil collected in March and July presented different chemical compositions. The oils from all species, except the one from A. occidentale, exhibited varying levels of antibacterial activity against Staphylococcus aureus, Bacillus cereus and Escherichia coli. Oil extracted in July from S. terebinthifolius was more active against all bacterial strains than the corresponding oil extracted in March. The high antibacterial activity of the M. urundeuva oil could be ascribed to its high δ-3-carene content. The amounts of MDA generated within bacterial cells indicate that the volatile oils induce lipid peroxidation. The results suggest that one putative mechanism of antibacterial action of these volatile oils is pro-oxidant damage within bacterial cell membrane explaining in part their preservative properties

Essential oils from pequi fruits from the brazilian Cerrado ecosystem

The composition of the essential oils of pequi fruits gathered from the Brazilian Cerrado ecosystem in the states of Maranhão (MA), Minas Gerais (MG) and Tocantins (TO) was investigated. The oils were obtained by steam distillation, and each component was speciated using GC-MS. The oil content varied from 0.13% to 1.15%. Interestingly, the major substance found within samples from two of the states was ethyl hexanoate (MA, MG), whereas isopropyl hexanoate and isopentyl-2-methylbutanoate were specific for the samples from TO. Both principal components analysis (PCA) and hierarchical cluster analysis (HCA) were used for exploratory analysis of the oils, and, consequently, the pequi fruits were classified according to their place of origin. The PCA showed that 51.5% of the variance accumulated in the PC1 and PC3, and the group formation obtained using HCA confirmed that the oil composition is influenced by geographic and/or plant genetic factors. Such analyses could assist in the selection of more flavoursome and healthy variants of pequi