Phytochemical profiling and isolation of bioactive compounds from Leucosidea sericea (Rosaceae)

In the study, ultra-performance liquid chromatography–quadrupole time-of-flight–mass spectrometry analysis of Leucosidea sericea leaf and stem extracts led to the identification of various classes of compounds. Further chromatographic purifications resulted in the isolation of 22 compounds that consisted of a new triterpenoid named leucosidic acid A (1), an acetophenone derivative 2, a phloroglucinol derivative 3, three chromones 4–6, seven pentacyclic triterpenoids 7–13, a phytosterol glucoside 14, a flavonoid 15, and seven flavonoid glycosides 16–22. Nineteen of these compounds including the previously undescribed triterpenoid 1 are isolated for the first time from L. sericea. The structures of the isolated compounds were assigned based on their high-resolution mass spectrometry and nuclear magnetic resonance data. Some of the isolated triterpenoids were evaluated for inhibitory activity against α-amylase, α-glucosidase, and pancreatic lipase. Of the tested compounds, 1-hydroxy-2-oxopomolic acid (7) and pomolic acid (13) showed higher potency on α-glucosidase than acarbose, which is used as a positive control in this study. The two compounds inhibited α-glucosidase with IC50 values of 192.1 ± 13.81 and 85.5 ± 6.87 μM, respectively.National Research Foundation of South Africa, University of Pretoria and South African Nuclear Energy Corporation Ltd.http://pubs.acs.org/journal/acsodfBiochemistryChemistryGeneticsMicrobiology and Plant Patholog

Triterpenoids from Protorhus longifolia exhibit hypocholesterolemic potential via regulation of cholesterol biosynthesis and stimulation of low-density lipoprotein uptake in HepG2 cells

The increasing incidence of hypercholesterolemia-related diseases even in the presence of the currently available cholesterol-lowering drugs indicates a need to discover new therapeutic drugs. This study aimed to investigate the hypocholesterolemic potential of two triterpenoids isolated from Protorhus longifolia stem bark. In silico techniques and in vitro enzyme assays were used to evaluate the potential inhibition of cholesterol esterase and HMGCoA reductase by the triterpenoids (ARM-2 and RA-5). The toxicity, modulation of low-density lipoprotein (LDL) uptake, and associated gene expression were determined in HepG2 hepatocytes. In silico molecular docking revealed that ARM-2 compared with RA-5 has a relatively stronger binding affinity for both enzymes. Both triterpenoids further demonstrated promising in silico drug-likeness properties and favorable ADMET profiles characterized by high intestinal absorption and lack of CYP450 enzyme inhibition. The compounds further showed, to varying degrees of efficacy, inhibition of cholesterol micellization as well as both cholesterol esterase and HMG-CoA reductase activities with IC50 values ranging from 16.4 to 41.1 μM. Moreover, enhanced hepatic cellular LDL uptake and the associated upregulation of the LDL-R and SREBP-2 gene expression were observed in the triterpenoid-treated HepG2 cells. It is evident that the triterpenoids, especially ARM-2, possess hypocholesterolemic properties, and these molecules can serve as leads or structural templates for the development of new hypocholesterolemic drugs.http://pubs.acs.org/journal/acsodfam2024AnatomyBiochemistryGeneticsMicrobiology and Plant PathologyNon

Antiproliferative Activity of Buddleja saligna (Willd.) against Melanoma and In Vivo Modulation of Angiogenesis

Funding Information: This research was funded by the University of Pretoria, the National Research Foundation-DAAD (SFD13080220333), the Department of Science and Innovation (DST/CON 0059/2019), the Innovation Hub, L’Oréal-UNESCO and FCT-MCTES (UIDP/04378/2020 and UIDB/04378/2020). Publisher Copyright: © 2022 by the authors.Melanoma cells secrete pro-angiogenic factors, which stimulates growth, proliferation and metastasis, and therefore are key therapeutic targets. Buddleja saligna (BS), and an isolated triterpenoid mixture (DT-BS-01) showed a fifty percent inhibitory concentration (IC50) of 33.80 ± 1.02 and 5.45 ± 0.19 µg/mL, respectively, against melanoma cells (UCT-MEL-1) with selectivity index (SI) values of 1.64 and 5.06 compared to keratinocytes (HaCat). Cyclooxygenase-2 (COX-2) inhibition was observed with IC50 values of 35.06 ± 2.96 (BS) and 26.40 ± 4.19 µg/mL (DT-BS-01). BS (30 µg/mL) significantly inhibited interleukin (IL)-6 (83.26 ± 17.60%) and IL-8 (100 ± 0.2%) production, whereas DT-BS-01 (5 µg/mL) showed 51.07 ± 2.83 (IL-6) and 0 ± 6.7% (IL-8) inhibition. Significant vascular endothelial growth factor (VEGF) inhibition, by 15.84 ± 4.54 and 12.21 ± 3.48%, respectively, was observed. In the ex ovo chick embryo yolk sac membrane assay (YSM), BS (15 µg/egg) significantly reduced new blood vessel formation, with 53.34 ± 11.64% newly formed vessels. Silver and palladium BS nanoparticles displayed noteworthy SI values. This is the first report on the significant anti-angiogenic activity of BS and DT-BS-01 and should be considered for preclinical trials as there are currently no US Food and Drug Administration (FDA) approved drugs to inhibit angiogenesis in melanoma.publishersversionpublishe

In vitro antiproliferative activity of Ptaeroxylon obliquum leaf extracts, fractions and isolated compounds on several cancer cell lines

Several cancers are induced by microbial infections or chronic inflammation. Ptaeroxylon obliquum is traditionally used to treat various infections characterized by inflammation. The in vitro antiproliferative and antioxidant activity of P. obliquum leaf extracts, fractions and isolated compounds were determined. Antiproliferative activity was assessed against normal Vero cells, and several cancerous human cells, including human breast cancer (MCF-7), hepatocarcinoma (HepG2), lung adenocarcinoma (A549) and human cervical cancer cells (HeLa) using a colorimetric tetrazolium bromide assay. Radical scavenging activity was tested using the 2,2-diphenyl-1-instrpicrylhydrazyl (DPPH) and 2,2’-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays. Obliquumol, Omethylalloptaeroxylin and a mixture of lupeol and -amyrin were isolated from the chloroform fraction using silica gel open column chromatography. Acetone extracts were toxic to HepG2 cells with IC50 values from 8 to 200 g/mL but were less toxic to other cells with selectivity index as high as 14. Aqueous extracts and fractions were non-toxic at concentrations tested against all the cell lines (IC50 > 100 g/mL). Isolated compounds had IC50 values ranging from 52 to 539 g/mL and 189 to 247 g/mL against HepG2 and HeLa cells, respectively. Light microscopy showing changes in HepG2 and HeLa cell morphology supported the cytotoxicity of the acetone extracts. Water extracts scavenged ABTS and DPPH radicals with IC50 values as low as 29.06 g/mL and 43.4 g/mL. P. obliquum extracts may be useful as sources of anticancer therapy, as they have selective cytotoxicity against cancer cell lines.The University of Pretoria, National Research Foundation (NRF) and the Health and Welfare Sector Education and Training Authority (HWSETA).https://www.mdpi.com/journal/applsciam2023ChemistryParaclinical Science

Quantitative UPLC-MS/MS analysis of obliquumol from Ptaeroxylon obliquum (Thunb.) Radlk. extracts and biological activities of its semi-synthesised derivative ptaeroxylinol

Quantification of compounds in plant extracts is rarely conducted to determine variation in concentrations of bioactive constituents. The aim of the study was to develop a method using ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) to identify and quantify obliquumol (12-O-acetylptaeroxylinol) in Ptaeroxylon obliquum leaves collected from different localities in South Africa. Additionally, biological activity of a semi-synthesized derivative, ptaeroxylinol was investigated. Column chromatography was used to isolate obliquumol from P. obliquum leaves, and thereafter it was saponified to ptaeroxylinol. Ultra-performance liquid chromatography coupled to quadrupole time of flight mass spectrometry (UPLC-qTof-MS) was carried out on the different P. obliquum extracts to quantify obliquumol. A serial microdilution method was used to determine the minimum inhibitory concentration (MIC) against non-pathogenic mycobacteria and fungi. The cytotoxicity was determined using Vero monkey kidney and human liver (C3A) cells. A method was developed to isolate large quantities of obliquumol (0.14%) from dried P. obliquum leaves. The different P. obliquum acetone extracts had variable obliquumol concentrations between 0.1–38.5 µg/mg. Ptaeroxylinol had an MIC as low as 8 µg/mL and 16 µg/mL against Candida albicans ATCC 10,231 and Cryptococcus neoformans, respectively. With an IC50 of 85.7 μg/mL for Vero cells and 126.51 μg/mL for C3A cells, respectively, ptaeroxylinol had low cytotoxicity to the cells tested. A UPLC-MS/MS method was developed to quantify obliquumol content in the P. obliquum acetone extracts. Ptaeroxylinol had good activity against C. albicans (MIC = 8 µg/mL) and it appears that the cleavage of the acetoxy to alcohol group played a role in the antimicrobial activity.The National Research Foundation (NRF), South Africa.http://www.elsevier.com/locate/sajb2024-03-09hj2023ChemistryParaclinical Science

Antifungal compounds from the leaves of Rhynchosia minima

Rhynchosia minima, commonly known as jumby bean, is used as a remedy for respiratory ailments in various parts of the world. It is also used by South African traditional healers to treat heart or chest pain. This study aimed to investigate the bioactive constituents of the leaf extracts of R. minima against selected fungal isolates that have been identified as risk factors in respiratory illness. Rhynchosia minima leaves were extracted sequentially using hexane, dichloromethane, ethyl acetate and methanol in increasing order of polarity. The extracts were subjected to repeated chromatographic techniques, for phytochemical isolation. The extracts and isolated compounds were screened against Candida albicans and Cryptococcus neoformans by determining the minimum concentration that inhibited fungal growth. Six flavonoids, one norisoprenoid and one cyclitol were isolated and characterized by 1D and 2D NMR and HR-ESI-MS. The extracts obtained in the study had moderate to weak antifungal activities, with MICs ranging from 312.5 to 1250.0 μg/mL against both fungi. Four isolated compounds were also screened, with two of them exhibiting activity against C. albicans (MIC=6.25 μg/mL) that was comparable to amphotericin B, the positive control. These two compounds also had better antifungal potential against C. neoformans with an MIC=6.25 μg/mL, compared to the MIC of 12.5 μg/mL of amphotericin B. Seven of the eight isolated compounds were obtained from the extracts of Rhynchosia minima for the first time. Two of the isolated compounds demonstrated activity comparable or superior to amphotericin B activity. The notable potency displayed by these compounds warrants further investigation on their development as antifungal agents.The National Research Foundation, Indigenous Knowledge System) South Africa and the University of Pretoria.https://onlinelibrary.wiley.com/journal/16121880hj2023ChemistryParaclinical Science

In Vitro Antiproliferative Activity of <i>Ptaeroxylon obliquum</i> Leaf Extracts, Fractions and Isolated Compounds on Several Cancer Cell Lines

Several cancers are induced by microbial infections or chronic inflammation. Ptaeroxylon obliquum is traditionally used to treat various infections characterized by inflammation. The in vitro antiproliferative and antioxidant activity of P. obliquum leaf extracts, fractions and isolated compounds were determined. Antiproliferative activity was assessed against normal Vero cells, and several cancerous human cells, including human breast cancer (MCF-7), hepatocarcinoma (HepG2), lung adenocarcinoma (A549) and human cervical cancer cells (HeLa) using a colorimetric tetrazolium bromide assay. Radical scavenging activity was tested using the 2,2-diphenyl-1-instrpicrylhydrazyl (DPPH) and 2,2’-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays. Obliquumol, O-methylalloptaeroxylin and a mixture of lupeol and β-amyrin were isolated from the chloroform fraction using silica gel open column chromatography. Acetone extracts were toxic to HepG2 cells with IC50 values from 8 to 200 µg/mL but were less toxic to other cells with selectivity index as high as 14. Aqueous extracts and fractions were non-toxic at concentrations tested against all the cell lines (IC50 > 100 µg/mL). Isolated compounds had IC50 values ranging from 52 to 539 µg/mL and 189 to 247 µg/mL against HepG2 and HeLa cells, respectively. Light microscopy showing changes in HepG2 and HeLa cell morphology supported the cytotoxicity of the acetone extracts. Water extracts scavenged ABTS and DPPH radicals with IC50 values as low as 29.06 µg/mL and 43.4 µg/mL. P. obliquum extracts may be useful as sources of anticancer therapy, as they have selective cytotoxicity against cancer cell lines

Fractions and isolated compounds from oxyanthus speciosus subsp. stenocarpus (Rubiaceae) have promising antimycobacterial and intracellular activity

BACKGROUND : Tuberculosis is a deadly disease caused by Mycobacterium species. The use of medicinal plants is an ancient global practice for the treatment and prevention of diverse ailments including tuberculosis. The aim of this study was to isolate and characterize antimycobacterial compounds by bioassay-guided fractionation of the acetone leaf extract of Oxyanthus speciosus. METHODS: A two-fold serial microdilution method was used to determine the minimum inhibitory concentration (MIC) against mycobacteria. Cytotoxicity and nitric oxide inhibitory activity of the isolated compounds was determined to evaluate in vitro safety and potential anti-inflammatory activity. Intracellular efficacy of the crude extract against Mycobacterium-infected macrophages was also determined. RESULTS : Two compounds were isolated and identified as lutein (1) and rotundic acid (2). These had good antimycobacterial activity against the four mycobacteria tested with MIC values ranging from 0.013 to 0.1 mg/mL. Rotundic acid had some cytotoxicity against C3A human liver cells. Lutein was not cytotoxic at the highest tested concentration (200 μg/mL) and inhibited nitric oxide production in RAW 264.7 macrophages by 94% at a concentration of 25 μg/mL. The acetone crude extract (120 μg/mL) of O. speciosus had intracellular antimycobacterial activity, reducing colony forming units by more than 90%, displaying bactericidal efficacy in a dose and time-dependent manner. CONCLUSION : This study provides good proof of the presence of synergism between different compounds in extracts and fractions. It is also the first report of the antimycobacterial activity of lutein and rotundic acid isolated from Oxyanthus speciosus. The promising activity of the crude extract of O. speciosus both in vitro and intracellularly in an in vitro macrophage model suggests its potential for development as an anti- tuberculosis (TB) herbal medicine.The South African Medical Research Council (SIR funding to LJM) and the National Research Foundation (NRF), South Africa. Funding was supplied by the National Research Foundation to LJ McGaw and JN Eloff (Grant No 81010).https://bmccomplementalternmed.biomedcentral.comam2019ChemistryParaclinical Science

Bioassay-guided isolation and identification of gametocytocidal compounds from Artemisia afra (Asteraceae)

BACKGROUND : Optimal adoption of the malaria transmission-blocking strategy is currently limited by lack of safe and efficacious drugs. This has sparked the exploration of different sources of drugs in search of transmission-blocking agents. While plant species have been extensively investigated in search of malaria chemotherapeutic agents, comparatively less effort has been channelled towards exploring them in search of transmission-blocking drugs. Artemisia afra (Asteraceae), a prominent feature of South African folk medicine, is used for the treatment of a number of diseases, including malaria. In search of transmission-blocking compounds aimed against Plasmodium parasites, the current study endeavoured to isolate and identify gametocytocidal compounds from A. afra. METHODS : A bioassay-guided isolation approach was adopted wherein a combination of solvent–solvent partitioning and gravity column chromatography was used. Collected fractions were continuously screened in vitro for their ability to inhibit the viability of primarily late-stage gametocytes of Plasmodium falciparum (NF54 strain), using a parasite lactate dehydrogenase assay. Chemical structures of isolated compounds were elucidated using UPLC-MS/MS and NMR data analysis. RESULTS : Two guaianolide sesquiterpene lactones, 1α,4α-dihydroxybishopsolicepolide and yomogiartemin, were isolated and shown to be active ( IC50 < 10 μg/ml; ~ 10 μM) against both gametocytes and intra-erythrocytic asexual P. falciparum parasites. Interestingly, 1α,4α-dihydroxybishopsolicepolide was significantly more potent against late-stage gametocytes than to early-stage gametocytes and intra-erythrocytic asexual P. falciparum parasites. Additionally, both isolated compounds were not overly cytotoxic against HepG2 cells in vitro. CONCLUSION : This study provides the first instance of isolated compounds from A. afra against P. falciparum gametocytes as a starting point for further investigations on more plant species in search of transmission-blocking compounds.Additional file 1: Table S1. Inhibition of in vitro viability of late stage gametocytes of Plasmodium falciparum (NF54 strain) by crude extract and fractions of Artemisia afra. Table S2. Inhibition of Plasmodium falciparum late gametocyte stages by fractions from column 1. Table S3. IC50 values of Artemisia afra chloroform fraction, compounds 1 and 2 on intra-erythrocytic asexuals, early gametocytes and late stage gametocytes. Fig. S1. Base Peak Ion chromatograms from UPLC-MS analysis using ESI +ve mode for fractions A) F10, B) F11, C) F13 and D) F19. Fig. S2. Full dose-response curve plots for artemisinin (ART) and methylene blue (MB) against latestage Plasmodium falciparum gametocytes.The South African Medical Research Council (SAMRC) Strategic Health Initiatives Partnerships (MRC-SHIP) and the South African Research Chairs Initiative of the Department of Science and Technology, administered through the South African National Research Foundation (NRF) to LB (UID84627). VJM is supported by a grant from the NRF (Grant Number 98988).http://www.malariajournal.comam2019BiochemistryChemistryGeneticsMicrobiology and Plant PathologyParaclinical Science