Molecular Dynamics Study on Selected Bioactive Phytochemicals as Potential Inhibitors of HIV-1 Subtype C Protease.

Acquired immunodeficiency syndrome (AIDS), one of the deadliest global diseases, is caused by the Human Immunodeficiency Virus (HIV). To date, there are no known conventional drugs that can cure HIV/AIDS, and this has prompted continuous scientific efforts in the search for novel and potent anti-HIV therapies. In this study, molecular dynamics simulation (MDS) and computational techniques were employed to investigate the inhibitory potential of bioactive compounds from selected South African indigenous plants against HIV-1 subtype C protease (HIVpro). Of the eight compounds (CMG, MA, UA, CA, BA, UAA, OAA and OA) evaluated, only six (CMG (-9.9 kcal/mol), MA (-9.3 kcal/mol), CA (-9.0 kcal/mol), BA (-8.3 kcal/mol), UAA (-8.5 kcal/mol), and OA (-8.6 kcal/mol)) showed favourable activities against HIVpro and binding landscapes like the reference FDA-approved drugs, Lopinavir (LPV) and Darunavir (DRV), with CMG and MA having the highest binding affinities. Using the structural analysis (root-mean-square deviation (RMSD), fluctuation (RMSF), and radius of gyration (RoG) of the bound complexes with HIVpro after 350 ns, structural evidence was observed, indicating that the six compounds are potential lead candidates for inhibiting HIVpro. This finding was further corroborated by the structural analysis of the enzyme-ligand complexe systems, where structural mechanisms of stability, flexibility, and compactness of the study metabolites were established following binding with HIVpro. Furthermore, the ligand interaction plots revealed that the metabolites interacted hydrophobically with the active site amino residues, with identification of other key residues implicated in HIVpro inhibition for drug design. Overall, this is the first computational report on the anti-HIV-1 activities of CMG and MA, with efforts on their in vitro and in vivo evaluations underway. Judging by the binding affinity, the degree of stability, and compactness of the lead metabolites (CMG, MA, CA, BA, OA, and UAA), they could be concomitantly explored with conventional HIVpro inhibitors in enhancing their therapeutic activities against the HIV-1 serotype.

Underutilized legumes, Cajanus cajan and Glycine max may bring about antisickling effect in sickle cell disease by modulation of redox homeostasis in sickled erythrocytes and alteration of its functional chemistry.

The antisickling and anti-oxidative effect of the Cajanus cajan, Glycine max, and their blends were investigated in sickled erythrocytes. The powdered samples were analyzed for their nutritional and anti-nutritional constituents. Their aqueous extracts were analyzed for in vitro antioxidant activities. The extracts were incubated with sickled erythrocytes at 37°C for 6 hours and the antisickling effect examined via microscopic analysis. The blend was the most active and its incubated cells were subjected to anti-oxidative analysis which covers for GSH, SOD, catalase, and lipid peroxidation (LPO). Chemical functional group of the treated cells was analyzed with FTIR spectroscopy. The in silico binding of the predominant amino acid to hemoglobin was also investigated. An increased concentration of leucine was observed in the blend compared to that of C. cajan and G. max, respectively. Vitamins C, B6, and B9 were the only vitamins observed in the blend. Phytate and oxalate were present in all samples. All extracts displayed significant (p < .05) scavenging activities. Treatment with the blend exacerbated SOD and catalase activities as well as the GSH level, while suppressing LPO. FTIR analysis of the treated cells showed the presence of hydrophobic functional groups. Leucine was the predominant amino acid, and it showed a potent molecular interaction with HIS-87 residue of the alpha chain of 1HCO. C. cajan and G. max blend inhibited sickling activities of sickle erythrocytes, while concomitantly exacerbating their endogenous antioxidant enzymes activity and modification of the functional chemistry. PRACTICAL APPLICATIONS: Cajanus cajan and Glycine max are among the common underutilized legumes in Nigeria. Aside their nutritional properties, these legumes have been used from time immemorial for the treatment and management of various ailments. Sickle cell anemia is a class of hemoglobinopathy common in Sub-Saharan Africa. There have been concerns about its treatment owing to the increasing scourge of the disease coupled to the financial burden of its management. This study reports the ability of the potentials of the legumes to prevent sickling activities of sickled erythrocytes and the possible biochemical mechanism involved.

Molecular modelling identification of phytocompounds from selected African botanicals as promising therapeutics against druggable human host cell targets of SARS-CoV-2.

The coronavirus disease 2019 (COVID-19), caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), is highly pathogenic and transmissible. It is mediated by the binding of viral spike proteins to human cells via entry and replication processes involving human angiotensin converting enzyme-2 (hACE2), transmembrane serine protease (TMPRSS2) and cathepsin L (Cath L). The identification of novel therapeutics that can modulate viral entry or replication has been of research interest and would be germane in managing COVID-19 subjects. This study investigated the structure-activity relationship inhibitory potential of 99 phytocompounds from selected African botanicals with proven therapeutic benefits against respiratory diseases focusing on SARS-CoV-2's human cell proteins (hACE2, TMPRSS2, and Cathepsin L) as druggable targets using computational methods. Evaluation of the binding energies of the phytocompounds showed that two compounds, Abrusoside A (-63.393 kcal/mol) and Kaempferol-3-O-rutinoside (-58.939 kcal/mol) had stronger affinity for the exopeptidase site of hACE2 compared to the reference drug, MLN-4760 (-54.545 kcal/mol). The study further revealed that Verbascoside (-63.338 kcal/mol), Abrectorin (-37.880 kcal/mol), and Friedelin (-36.989 kcal/mol) are potential inhibitors of TMPRSS2 compared to Nafamostat (-36.186 kcal/mol), while Hemiphloin (-41.425 kcal/mol), Quercetin-3-O-rutinoside (-37.257 kcal/mol), and Myricetin-3-O-galactoside (-36.342 kcal/mol) are potential inhibitors of Cathepsin L relative to Bafilomycin A1 (-38.180 kcal/mol). The structural analysis suggests that these compounds do not compromise the structural integrity of the proteins, but rather stabilized and interacted well with the active site amino acid residues critical to inhibition of the respective proteins. Overall, the findings from this study are suggestive of the structural mechanism of inhibitory action of the identified leads against the proteins critical for SARS-CoV-2 to enter the human host cell. While the study has lent credence to the significant role the compounds could play in developing potent SARS-CoV-2 candidate drugs against COVID-19, further structural refinement, and modifications of the compounds for subsequent in vitro as well as preclinical and clinical evaluations are underway.

Astaxanthin-Mediated Bacterial Lethality: Evidence from Oxidative Stress Contribution and Molecular Dynamics Simulation.

The involvement of cellular oxidative stress in antibacterial therapy has remained a topical issue over the years. In this study, the contribution of oxidative stress to astaxanthin-mediated bacterial lethality was evaluated in silico and in vitro. For the in vitro analysis, the minimum inhibitory concentration (MIC) of astaxanthin was lower than that of novobiocin against Staphylococcus aureus but generally higher than those of the reference antibiotics against other test organisms. The level of superoxide anion of the tested organisms increased significantly following treatment with astaxanthin when compared with DMSO-treated cells. This increase compared favorably with those observed with the reference antibiotics and was consistent with a decrease in the concentration of glutathione (GSH) and corresponding significant increase in ADP/ATP ratio. These observations are suggestive of probable involvement of oxidative stress in antibacterial capability of astaxanthin and in agreement with the results of the in silico evaluations, where the free energy scores of astaxanthins' complexes with topoisomerase IV ParC and ParE were higher than those of the reference antibiotics. These observations were consistent with the structural stability and compactness of the complexes as astaxanthin was observed to be more stable against topoisomerase IV ParC and ParE than DNA Gyrase A and B. Put together, findings from this study underscored the nature and mechanism of antibacterial action of astaxanthin that could suggest practical approaches in enhancing our current knowledge of antibacterial arsenal and aid in the novel development of alternative natural topo2A inhibitor.

Exploring the bioactivity of pentacyclic triterpenoids as potential antimycobacterial nutraceutics: Insights through comparative biomolecular modelling.

A group of bioactive compounds known as triterpenoids, which are often found in plant materials, have been tested to possess nutritional and pharmaceutical activity. These plant components are referred to as nutraceuticals, and are used as therapeutic agents. In this study, we explore the interactions of betulinic acid (BA), oleanolic acid (OA), ursolic acid (UA), and maslinic acid (MA) against FadA5. Studies have identified FadA5, a trifunctional enzyme-like thiolase, as a target towards Mycobacterium tuberculosis inhibition. The investigation involves molecular dynamics (MD) and hybrid quantum mechanics/molecular mechanics (QM/MM) applications. Analyses of the four pentacyclic triterpenoids binding to FadA5 showed appreciable bioactivity against FadA5. The application of two or more theoretical models to unravel ligand-enzyme binding energies can pave the way for accurate binding affinity prediction and validation.

Leptospermum petersonii as a Potential Natural Food Preservative.

Leptospermum petersonii (family Myrtaceae) is often cultivated for ornamental purposes but also serves as a rich source of bioactive essential oils. While several studies focused on the activities of the essential oils, this study analysed the potential of spent L. petersonii leaves as a natural food preservative. METHOD: We investigated the in vitro antioxidant and antimicrobial activities of crude L. petersonii extracts against activities of the purified isolated flavonoid, 6-methyltectochrysin, which was characterized using spectroscopic methods. The antioxidant assays followed ORAC, FRAP and TEAC tests. The antimicrobial activities of the extract and purified flavonoid were analysed against six multi-drug resistant microbial strains in broth dilution assays. RESULT: The results revealed that both the crude extracts and isolated 6-methyltectochrysin exhibited positive radical ion scavenging antioxidant potential, however the crude extract was about 6-fold more potent antioxidant than the purified 6-methyltectochrysin. The crude extract also showed strong antimicrobial activities against Bacillus cereus, and even more potent antimicrobial agent than the reference ampicillin antibiotic against Klebsiella pneumoniae subsp. pneumoniae. A higher resistance was observed for the tested Gram-negative strains than for the Gram-positive ones. 6-methyltectochrysin was generally inactive in the antimicrobial assays. CONCLUSION: The crude methanolic extract showed significant bioactivity which validates the medicinal relevance of the plant. The observed biological activities, especially against a notorious strain of B. cereus, suggest that L. petersonii could be a promising natural source of food preservatives.

Iso-Mukaadial Acetate from Warburgia salutaris Enhances Glucose Uptake in the L6 Rat Myoblast Cell Line.

Diabetes mellitus (DM) is a chronic metabolic disorder which has become a major risk to the health of humankind, as its global prevalence is increasing rapidly. Currently available treatment options in modern medicine have several adverse effects. Thus, there is an urgent need to develop alternative cost-effective, safe, and active treatments for diabetes. In this regard, medicinal plants provide the best option for new therapeutic remedies desired to be effective and safe. Recently, we focused our attention on drimane sesquiterpenes as potential sources of antimalarial and antidiabetic agents. In this study, iso-mukaadial acetate (Iso) (1), a drimane-type sesquiterpenoid from the ground stem bark of Warburgia salutaris, was investigated for glucose uptake enhancement in the L6 rat myoblast cell line. In vitro assays with L6 skeletal muscle cells were used to test for cytotoxicity, glucose utilisation, and western blot analysis. Additionally, the inhibition of carbohydrate digestive enzymes and 1,1-diphenyl-2- picrylhydrazyl (DPPH) scavenging activity were analysed in vitro. The cell viability effect of iso-mukaadial acetate was the highest at 3 µg/mL with a percentage of 98.4. Iso-mukaadial acetate also significantly and dose-dependently increased glucose utilisation up to 215.18% (12.5 µg/mL). The increase in glucose utilisation was accompanied by enhanced 5' adenosine monophosphate-activated protein kinase (AMPK)and protein kinase B (AKT) in dose-dependent manner. Furthermore, iso-mukaadial acetate dose-dependently inhibited the enzymes α-amylase and α-glucosidase. Scavenging activity against DPPH was displayed by iso-mukaadial acetate in a concentration-dependent manner. The findings indicate the apparent therapeutic efficacy of iso-mukaadial acetate isolated from W. salutaris as a potential new antidiabetic agent.

Isolation, characterization, and biological evaluation of a potent anti-malarial drimane sesquiterpene from Warburgia salutaris stem bark.

BACKGROUND: Malaria continues to be a global burden as the efficacy of most commercial anti-malarial drugs has been compromised by the evolution of parasite resistance. With the urgent need created for the development of alternative and more efficient anti-malarial drugs, this study focused on the evaluation of anti-malarial agents of the Warburgia salutaris stem bark. METHODS: The stem bark was extracted with dichloromethane followed by silica gel column chromatography that led to the isolation of iso-mukaadial acetate, a drimanoid sesquiterpene. This compound was characterized by spectroscopic analysis (1H NMR, 13C NMR, IR and MS), and its structure was confirmed by X-ray crystallography. In vitro anti-plasmodial activity was investigated using a chloroquine sensitive NF54 Plasmodium falciparum strain. Cytotoxicity was measured using the MTT assay on HEK239 and HEPG2 cell lines. Chloroquine-sensitive Plasmodium berghei was used to infect Sprague-Dawley rats for in vivo studies. The W. salutaris crude extract and iso-mukaadial acetate were administered orally at 0.5; 1.5, 2.5 and 5 mg/kg, chloroquine was used as the reference drug. Determination of percentage parasitaemia, haematological parameters, and rat body weights was done throughout the experimental study period. RESULTS: The crude extract and iso-mukaadial acetate showed very good activity on the inhibition of parasite growth (IC50 0.01 ± 0.30 µg/ml) and (IC50 0.44 ± 0.10 µg/ml), respectively, with iso-mukaadial acetate having cytotoxicity activity of 36.7 ± 0.8 and 119.2 ± 8.8 (µg/ml) on HEK293 and HEPG2 cells, respectively. The crude extract and iso-mukaadial acetate reduced percentage parasitaemia in a dose-dependent manner in comparison to the control. There were no significant differences in the haematological parameters in all the experimental groups in comparison to control group. This study proves that W. salutaris contains components (including iso-mukaadial acetate) that exhibit anti-malarial activity. This study scientifically validates the use of this plant in folk medicine. CONCLUSIONS: This study proves that Warburgia salutaris contains components (including iso-mukaadial acetate) that exhibit anti-malarial activity and scientifically validates the use of this plant in folk medicine.

Antimycobacterial, docking and molecular dynamic studies of pentacyclic triterpenes from Buddleja saligna leaves.

Buddleja saligna (family Buddlejaceae) is a medicinal plant endemic to South Africa. Two isomeric pentacyclic triterpenes, oleanolic acid and ursolic acid, were isolated from the leaves of B. saligna using silica gel column chromatography. Compounds oleanolic acid and ursolic acid were subjected to derivatization with acetic anhydride in the presence of pyridine to obtain oleanolic acid-3-acetate and ursolic acid-3-acetate, respectively. The structures of these compounds were fully characterized by detailed nuclear magnetic resonance (NMR) investigations, which included 1H and 13C NMR. Molecular docking studies predicted the free binding energy of the four triterpenes inside the steroid binding pocket of Mycobacterium tuberculosis fadA5 thiolase compared to a reported inhibitor. Thus, their ability to inhibit the growth of M. tuberculosis was predicted and was confirmed to possess significant antimycobacterial activity when tested against Mycobacterium smegmatis, M. tuberculosis H37Rv (ATCC 25177), clinical isolates of multi-drug-resistant M. tuberculosis (MDR-TB) and extensively drug-resistant M. tuberculosis (XDR-TB) using the Micro Alamar Blue Assay. Ursolic acid was isolated from this plant for the first time.

Guava leaves polyphenolics-rich extract inhibits vital enzymes implicated in gout and hypertension in vitro.

BACKGROUND/AIM: Elevated uric acid level, an index of gout resulting from the over-activity of xanthine oxidase (XO), increases the risk of developing hypertension. However, research has shown that plant-derived inhibitors of XO and angiotensin 1-converting enzyme (ACE), two enzymes implicated in gout and hypertension, respectively, can prevent or ameliorate both diseases, without noticeable side effects. Hence, this study characterized the polyphenolics composition of guava leaves extract and evaluated its inhibitory effect on XO and ACE in vitro. MATERIALS AND METHODS: The polyphenolics (flavonoids and phenolic acids) were characterized using high-performance liquid chromatography (HPLC) coupled with diode array detection (DAD). The XO, ACE, and Fe(2+)-induced lipid peroxidation inhibitory activities, and free radicals (2,2-diphenylpicrylhydrazyl [DPPH]* and 2,2´-azino-bis-3-ethylbenzthiazoline-6-sulphonic [ABTS]*(+)) scavenging activities of the extract were determined using spectrophotometric methods. RESULTS: Flavonoids were present in the extract in the order of quercetin > kaempferol > catechin > quercitrin > rutin > luteolin > epicatechin; while phenolic acids were in the order of caffeic acid > chlorogenic acid > gallic acids. The extract effectively inhibited XO, ACE and Fe(2+)-induced lipid peroxidation in a dose-dependent manner; having half-maximal inhibitory concentrations (IC50) of 38.24 ± 2.32 µg/mL, 21.06 ± 2.04 µg/mL and 27.52 ± 1.72 µg/mL against XO, ACE and Fe(2+)-induced lipid peroxidation, respectively. The extract also strongly scavenged DPPH* and ABTS*(+). CONCLUSION: Guava leaves extract could serve as functional food for managing gout and hypertension and attenuating the oxidative stress associated with both diseases.

Antibacterial and anti-biofilm activity of flavonoids and triterpenes isolated from the extracts of Ficus sansibarica Warb. subsp. sansibarica (Moraceae) extracts.

BACKGROUND: Ficus species are used in African traditional medicine in the treatment of a wide variety of ailments and diseases such as convulsive disorder, wound healing, gonorrhea, tuberculosis, diabetes, diarrhoeal infections, dysentery, malaria and HIV. The aim of this study was to isolate the phytochemical constituents in the plant and test them for their antibacterial activity. MATERIALS AND METHODS: The fruits, leaves and stem bark were extracted with organic solvents and the compounds in the extracts separated and purified by column chromatography before being identified by NMR spectroscopy and by comparison of the NMR data against values reported in the literature. The antibacterial activity of the pure compounds and extracts were tested using the disk diffusion method. RESULTS: Three triterpenes and three flavonoids: lupeol acetate (1); cycloart-23-ene-3,25-diol (2); ß-sitosterol (3); 5,7,4'-trihydroxyflavan-3-ol (4); epicatechin (5); and isovitexin (6) were isolated in this study. Antimicrobial activity was observed at 8 mg mL(-1) for Staphylococcus aureus ATCC 29213 with four of the six isolated compounds, with no activity being observed at 1 - 4 mg mL(-1) against Escherichia coli ATCC 25922, E. coli ATCC 35218 and S. aureus ATCC 43300. Epicatechin (5) was found to decrease adhesion of E. coli ATCC 25922 and S. aureus ATCC 29213. Decreased adhesion of S. aureus ATCC 29213 was also observed with 5,7,4'-trihydroxyflavan-3-ol (4) and isovitexin (6). CONCLUSIONS: The results of this study provide baseline information on F. sansibarica's potential validity in the treatment of infections associated with Gram-positive microorganisms.

Semi-synthesis of nitrogen derivatives of oleanolic acid and effect on breast carcinoma MCF-7 cells.

BACKGROUND: Oleanolic acid is a triterpenoid that has shown in vitro cytotoxic activity against human tumour cells and is known to be present in many higher plants. MATERIALS AND METHODS: Oleanolic acid is known to have some biological potential including anticancer property. Oleanolic acid was isolated from the ethyl acetate fraction of Syzygium aromaticum seed with an aim of dervitatising the functional group and evaluating the biological activities of the semi-synthesised compounds. Acylation of the alcohol functional group of the oleanolic acid afforded the opportunity of hydrazine reaction to give 3-acetoleanolic hydrazide. Further reaction of 3-acetoleanolic hydrazide with benzyladehyde, glacial acetic acid and methanol resulted in the synthesis of the corresponding 3-acetoxyoleanolic hydrazone. RESULTS: The semi-synthetic oleanolic acid derivatives did not exhibit enhanced cytotoxic activity over oleanolic acid itself. CONCLUSION: 3-acetoxyoleanolic hydrazide has a potent anticancer activity.

Anti-plasmodial activity of some Zulu medicinal plants and of some triterpenes isolated from them.

Mimusops caffra E. Mey. ex A.DC and Mimusops obtusifolia Lam (both members of the Sapotaceae family), and Hypoxis colchicifolia Bak (family Hypoxidaceae) are used by traditional healers in Zululand to manage malaria. Anti-plasmodial investigation of the crude extracts and some triterpenes isolated from the plants showed activity against a chloroquine sensitive (CQS) strain of Plasmodium falciparum (D10). Among the crude extracts the leaves of M. caffra exhibited the highest activity, with an IC50 of 2.14 µg/mL. The pentacyclic tritepenoid ursolic acid (1), isolated from the leaves of M. caffra was the most active compound (IC50 6.8 µg/mL) as compared to taraxerol (2) and sawamilletin (3) isolated from the stem bark of M. obtusifolia (IC50 > 100). Chemical modification of the ursolic acid (1) to 3ß-acetylursolic acid (4) greatly enhanced its anti-plasmodial activity. Compound 4 reduced parasitaemia against Plasmodium berghei by 94.01% in in vivo studies in mice. The cytotoxicity of 3ß-acetylursolic acid (IC50) to two human cell lines (HEK293 and HepG2) was 366.00 µg/mL and 566.09 µg/mL, respectively. The results validate the use of these plants in folk medicine.

Syntheses and biological activity of some derivatives of C-9154 antibiotic.

This research was undertaken to design several new antibiotics, by structurally modifying the C-9154 antibiotic, simultaneously improving its activity and lowering toxicity. This was achieved by synthesizing an analogue to the C-9154 antibiotic and seven derivatives of this analogue. The approach was to significantly reduce the polarity of the synthesized analogue in the derivatives to achieve increased permeability across cell membranes by conversion of the highly polar carboxylic group to an ester functional group. The compounds were fully characterized using infrared, GC-MS, and 1D and 2D NMR experiments. The in vitro biological activity of the compounds showed that the derivatives were more active than the analogue as was anticipated and both were more active than the standard drugs used for comparison. Work is ongoing to establish applications for the compounds as antiplasmodials, antivirals, anticancers/tumours, antitrypanosomiasis, anthelminthic, and as general antibiotics for human, veterinary, and even agricultural use as they had marked effect on both Gram-positive and Gram-negative bacteria and some fungi.

Syntheses and in vitro biological activity of some derivatives of C-9154 antibiotic.

In our continued attempts at designing new antibiotics based on the structure of the C-9154 antibiotic, to simultaneously improve activity and lower toxicity, an analogue to the C-9154 antibiotic and six derivatives of this analogue were synthesized. The approach was to significantly reduce the polarity of the synthesized analogue in the derivatives to achieve increased permeability across cell membranes by conversion of the highly polar carboxylic group to an ester functional group. The compounds were synthesized using a two-step reaction which involved an additional reaction between benzyl amine and maleic anhydride and then conversion of the terminal carboxylic acid functional group to an ester functional group using a thionyl chloride mediated esterification reaction. The compounds were fully characterized using Infrared, GC-MS, and 1D and 2D NMR experiments. The in vitro biological activity of the compounds showed that the derivatives were more active than the analogues as was anticipated with minimum inhibitory concentration in the range 0.625-5 µg/mL. The analogue had minimum inhibitory concentration in the range 2.5-10 µg/mL. These values are significantly better than that obtained for the original C-9154 antibiotic which had activity in the range 10->100 µg/mL.

Antimicrobial activities of hexane extract and decussatin from stembark extract of Ficus congensis.

Ficus congensis (Moraceae) is used traditionally in the treatment of various diseases including infectious diseases, infertility, and gastrointestinal disorders. Investigation of hexane extract of the stem bark using chromatographic techniques led to isolation of a xanthone, 1-hydroxy-3,7,8-trimethoxyxanthone (Decussatin). The compound was elucidated based on spectroscopic methods such as nuclear magnetic resonance (NMR), UV, IR, and mass spectrometry (MS). Decussatin and the hexane extract were screened in vitro for antibacterial and antifungal activities using broth microdilution (MHB) and disc Agar diffusion (DAD) techniques against Escheichia coli, Bacilus substilis, Klebsiela pneumonia, Staphylococcus aureus, Aspergillus fumigatus, Trichophyton mentagrophytes, Trichophyton rubrum and Candida albicans. Hexane extracts showed potent antibacterial activity against E. coli and B. subtilis with minimum inhibitory concentrations (MIC) of 8 mg/mL and 5 mg/mL, respectively, while Decussatin of the highest concentration (8 mg/mL) used in this study showed no appreciable antimicrobial activity. Only hexane extract was active against C. albicans with a MIC of 1 mg/mL.

Chemical composition and antibacterial activity of the essential oils of Callistemon citrinus and Callistemon viminalis from South Africa.

The chemical composition and the antibacterial activity of the essential oils obtained by hydrodistillation from the leaves of Callistemon citrinus and Callistemon viminalis were analyzed by GC and GC/MS. Twenty-four and twelve components were identified for C. citrinus and C. viminalis, representing 92.0% and 98.3% of the total oils. The major components of C. citrinus and C. viminalis were 1,8-cineole (61.2% and 83.2%) and alpha-pinene (13.4% and 6.4%), respectively. The in vitro antibacterial activity of the essential oils was studied against 12 bacteria strains using disc diffusion and broth microdilution methods. The oils exhibited strong zone of inhibitions against some bacteria such as S. faecalis (20.3-24.0 mm), both strains of S. aureus (23.0-26.3 mm), B. cereus (17.3-19.0 mm) and S. macrcesens (11.3-23.7 mm) when compared to standard antibiotics gentamycin and tetracycline used as controls. Expect for P. aeruginosa and S. macrcescens, the MIC values of both essential oils ranged from 0.31-2.50 mg/mL.

Typhaphthalide and typharin, two phenolic compounds from Typha capensis.

Two new phenolics, named typhaphthalide (a benzylphthalide) and typharin (an isocoumarin) plus sitosterol were isolated and identified from the hexane extract of the rhizomes of Typha capensis. The acetone extract yielded afzelechin, epiafzelechin, and catechin.