Predictive classifier models built from natural products with antimalarial bioactivity using machine learning approach.

In view of the vast number of natural products with potential antiplasmodial bioactivity and cost of conducting antiplasmodial bioactivity assays, it may be judicious to learn from previous antiplasmodial bioassays and predict bioactivity of these natural products before experimental bioassays. This study set out to harness antimalarial bioactivity data of natural products to build accurate predictive models, utilizing classical machine learning approaches, which can find potential antimalarial hits from new sets of natural products. Classical machine learning approaches were used to build four classifier models (Naïve Bayesian, Voted Perceptron, Random Forest and Sequence Minimization Optimization of Support Vector Machines) from bioactivity data of natural products with in-vitro antiplasmodial activity (NAA) using a combination of the molecular descriptors and two-dimensional molecular fingerprints of the compounds. Models were evaluated with an independent test dataset. Possible chemical features associated with reported antimalarial activities of the compounds were also extracted. From the results, Random Forest (accuracy 82.81%, Kappa statistics 0.65 and Area under Receiver Operating Characteristics curve 0.91) and Sequential Minimization Optimization (accuracy 85.93%, Kappa statistics 0.72 and Area under Receiver Operating Characteristics curve 0.86) showed good predictive performance for the NAA dataset. The amine chemical group (specifically alkyl amines and basic nitrogen) was confirmed to be essential for antimalarial activity in active NAA dataset. This study built and evaluated classifier models that were used to predict the antiplasmodial bioactivity class (active or inactive) of a set of natural products from interBioScreen chemical library.

Short communication. Challenges relating to comparison of flavonoid glycosides dissolution profiles from Sutherlandia frutescens products.

Unlike the case of conventional drug formulations, dissolution tests have hitherto not been required for herbal medicinal products commercially available in South Africa. This study investigated dissolution of the South African Sutherlandia frutescens using selected flavonoid glycosides as marker compounds. Dissolution of markers was assessed in three dissolution media at pH 1.2, 4.5 and 6.8, and samples were analysed using a validated HPLC method. The dissolution profile of each marker varied for the different materials investigated. All three media utilised showed differences in flavonoid glycoside dissolution between the S. frutescens products evaluated, with f2 values < 50 for comparison of flavonoid dissolution from any two of the materials. Dissolution of S. frutescens materials could thus be characterised using the markers in all the media tested. This tool may be employed in the future for comparison of orally administered S. frutescens products, provided between- batch variability is evaluated and found less than between-sample variability.

Consumption of Sutherlandia frutescens by HIV-Seropositive South African Adults: An Adaptive Double-Blind Randomized Placebo Controlled Trial.

BACKGROUND: Sutherlandia frutescens (L.) R. Br. is widely used as an over the counter complementary medicine and in traditional medications by HIV seropositive adults living in South Africa; however the plant's safety has not been objectively studied. An adaptive two-stage randomized double-blind placebo controlled study was used to evaluate the safety of consuming dried S. frutescens by HIV seropositive adults with CD4 T-lymphocyte count of >350 cells/µL. METHODS: In Stage 1 56 participants were randomized to S. frutescens 400, 800 or 1,200 mg twice daily or matching placebo for 24 weeks. In Stage 2 77 additional participants were randomized to either 1,200 mg S. frutescens or placebo. In the final analysis data from Stage 1 and Stage 2 were combined such that 107 participants were analysed (54 in the S. frutescens 1,200 mg arm and 53 in the placebo arm). RESULTS: S. frutescens did not change HIV viral load, and CD4 T-lymphocyte count was similar in the two arms at 24 weeks; however, mean and total burden of infection (BOI; defined as days of infection-related events in each participant) was greater in the S. frutescens arm: mean (SD) 5.0 (5.5) vs. 9.0 (12.7) days (p = 0.045), attributed to two tuberculosis cases in subjects taking isoniazid preventive therapy (IPT). CONCLUSION: A possible interaction between S. frutescens and IPT needs further evaluation, and may presage antagonistic interactions with other herbs having similar biochemical (antioxidant) properties. No other safety issues relating to consumption of S. frutescens in this cohort were identified. TRIAL REGISTRATION: ClinicalTrials.gov NCT00549523.

Pulmonary effects and disposition of luteolin and Artemisia afra extracts in isolated perfused lungs.

ETHNOPHARMACOLOGICAL RELEVANCE: Artemisia afra (Asteraceae) is a traditional medicinal plant frequently used in steam inhalation form to treat respiratory conditions. AIM OF THE STUDY: Quantify luteolin content in Artemisia afra dried crude and aqueous extract. Evaluate the pulmonary effects of Artemisia afra steam inhalation, nebulized Artemisia afra extract and luteolin in isolated perfused lungs (IPL). Evaluate the pulmonary disposition of intravenously administered luteolin. MATERIALS AND METHODS: HPLC was used to quantify luteolin in Artemisia afra extracts. A modified version of the IPL was used to determine the effects of Artemisia afra steam inhalation, nebulized luteolin, and nebulized aqueous leaf extract on lung function, as well as the pulmonary disposition of IV luteolin. RESULTS: Artemisia afra extract contained significantly higher luteolin levels than the crude dried leaves. Inhaled Artemisia afra steam, and nebulized luteolin, and Artemisia afra extract and IV luteolin produced significant dose-dependent improvements in lung function, with nebulized Artemisia afra producing the greatest improvements. Nebulisation with Artemisia afra extract yielded higher quantities of luteolin than luteolin nebulisation. CONCLUSION: Results verify the traditional use of inhalation of Artemisia afra steam, although nebulized luteolin and aqueous extract are better alternatives. Luteolin significantly contributes to the bronchodilatory effects of Artemisia afra.

Effect of the plant matrix on the uptake of luteolin derivatives-containing Artemisia afra aqueous-extract in Caco-2 cells.

AIM OF THE STUDY: Luteolin is a major flavonoid constituent and a primary candidate that might contribute to the claimed in vivo protective effects of Artemisia afra (Jacq. Ex. Willd). However, an exhaustive search yielded no literature evidence on the absorption, metabolism and fate of this flavonoid from the traditional plant preparation. The purpose of this study was to investigate the effect of the plant matrix on the uptake of luteolin derivatives from Artemisia afra aqueous extract in human intestinal epithelial Caco-2 cells. MATERIALS AND METHODS: Cell monolayers were incubated with 5, 10 and 20 microg/ml doses of luteolin aglycone, luteolin-7-0-glucoside, un-hydrolyzed or acid-hydrolyzed Artemisia afra extracts, and samples of 150 microl each were collected from both apical and basolateral sides of cells at 30, 60 and 120 min for HPLC and LC-MS analyses. RESULTS: After 1-h exposure, the uptake of luteolin aglycone and luteolin-7-0-glucoside from the un-hydrolyzed and acid-hydrolyzed extracts was significantly faster and quantitatively higher (i.e. >77% vs. <25% of the initial doses over the first 30 min, p<0.05) than that from non-plant solutions. Apical to basolateral permeability coefficients for luteolin and its-7-0-glucoside in the extracts were 1.6- to 2-fold higher than that for the non-plant solutions. Glucuronidation was an important pathway of metabolism for luteolin in both non-plant and plant extract forms. CONCLUSIONS: Luteolin in Artemisia afra aqueous extract, regardless of its form (i.e. whether aglycone and 7-0-glucoside), is taken up better and more efficiently metabolized than the aglycone and 7-0-glucoside forms administered as pure solutions in Caco-2 cells. Flavonoid actives from Artemisia afra plant extracts and especially traditionally prepared dosage forms may thus have better bioavailability, and consequently greater in vivo potency, than that predicted from studies done using the pure solutions.

Flavonol glycosides from the south African medicinal plant Sutherlandia frutescens.

Phytochemical investigation of the leaves of Sutherlandia frutescens led to the isolation of four new 3-hydroxy-3-methylglutaroyl-containing flavonol glycosides, sutherlandins A-D ( 1- 4). Their structures were elucidated by chemical and spectroscopic methods as quercetin 3- O- beta- D-xylopyranosyl(1 --> 2)-[6- O-(3-hydroxy-3-methylglutaroyl)]- beta- D-glucopyranoside ( 1), quercetin 3- O- beta- D-apiofuranosyl(1 --> 2)-[6- O-(3-hydroxy-3-methylglutaroyl)]- beta- D-glucopyranoside ( 2), kaempferol 3- O- beta- D-xylopyranosyl(1 --> 2)-[6- O-(3-hydroxy-3-methylglutaroyl)]- beta- D-glucopyranoside ( 3), and kaempferol 3- O- beta- D-apiofuranosyl(1 --> 2)-[6- O-(3-hydroxy-3-methylglutaroyl)]- beta- D-glucopyranoside ( 4).

Efficacy of Artemisia afra phytotherapy in experimental tuberculosis.

Artemisia afra [Jacq] (Asteraceae) phytotherapy is widely used for its medicinal properties in traditional practices. In this study we investigated whether extracts of A. afra are capable of controlling mycobacterial replication. For Mycobacterium aurum cultured in the presence of aqueous-, methanol- and dichloromethane (DCM) extracts of A. afra we found that bacterial replication was inhibited by the dichloromethane extract only. Activity of the DCM extract was confirmed in dose-dependent studies against both M. aurum and M. tuberculosis with an IC(50) =270 microg/ml and IC(50) = 290microg/ml, respectively. Fractionation of the DCM extract and evaluation of its efficacy in vitro found that most of the antimycobacterial activity was associated with isolate fraction C8 that contained several sesquiterpene lactones, the most prominent of which are Artemin and Arsubin. Evaluation of the bactericidal efficacy in vitro showed that isolate fraction C8 reduced replication of M. aurum and M. tuberculosis in a dose-dependent manner with IC(50) =1.9 microg/ml and IC(50) = 2.0 microg/ml, respectively, and an MIC = 10 microg/ml. Further, isolate fraction C8 and the DCM extract was administered to M. tuberculosis-infected mice at a tolerated dose of 1000 microg/kg for up to 26 weeks and mycobacterial burdens compared to untreated-, INH/RIF treated- and aqueous-extract-treated animals to assess its bactericidal activity in vivo. Bacterial replication remained unaffected during treatment with either isolate fraction C8 or the DCM extract resulting in pulmonary and splenic bacilli burdens comparable to that of untreated mice. In contrast, INH/RIF treatment cleared M. tuberculosis infection after only 8 weeks to undetectable levels. Interestingly, treatment of M. tuberculosis-infected mice with aqueous extract of A. afra regulated pulmonary inflammation during early infection notwithstanding its inability to inhibit mycobacterial growth. This study clearly demonstrates that A. afra contains in vitro anti-mycobacterial activity, modulates pulmonary inflammation in early mycobacterial infection, and that the mouse experimental tuberculosis model may serve as a useful assay for evaluating the utility of phytotherapy.

Cycloartane glycosides from Sutherlandia frutescens.

Four new cycloartane glycosides, sutherlandiosides A-D (1-4), were isolated from the South African folk medicine Sutherlandia frutescens and their structures established by spectroscopic methods and X-ray crystallography as 1 S,3 R,24S,25-tetrahydroxy-7S,10S-epoxy-9,10- seco-9,19-cyclolanost-9(11)-ene 25-O-beta-D-glucopyranoside (1), 3R,7S,24S,25-tetrahydroxycycloartan-1-one 25-O-beta-D-glucopyranoside (2), 3R,24S,25-trihydroxycycloartane-1,11-dione 25-O-beta-D-glucopyranoside (3), and 7S,24S,25-trihydroxycycloart-2-en-1-one 25-O-beta-D-glucoyranoside (4). Compound 1 represents the first secocycloartane skeleton possessing a 7,10-oxygen bridge. Compounds 2- 4 are also the first examples of naturally occurring cycloartanes with a C-1 ketone functionality. Biosynthetic considerations and chemical evidence suggest that the presence of the C-1 ketone in 2 may facilitate the ring opening of the strained cyclopropane system.

A randomized, double-blind, placebo-controlled trial of Lessertia frutescens in healthy adults.

OBJECTIVES: Indigenous medicines are widely used throughout Africa, despite a lack of scientific evidence for their safety or efficacy. The aims of this study were: (a) to conduct a pilot study of the safety of a common indigenous South African phytotherapy, Lessertia frutescens (Sutherlandia), in healthy adults; and (b) to contribute to establishing procedures for ethical and scientifically rigorous clinical trials of African indigenous medicines. DESIGN: A randomized, double-blind, placebo-controlled trial of Sutherlandia leaf powder in healthy adults. SETTING: Tiervlei Trial Centre, Karl Bremer Hospital, Bellville, South Africa. PARTICIPANTS: 25 adults who provided informed consent and had no known significant diseases or allergic conditions nor clinically abnormal laboratory blood profiles during screening. INTERVENTION: 12 participants randomized to a treatment arm consumed 400 mg capsules of Sutherlandia leaf powder twice daily (800 mg/d). 13 individuals randomized to the control arm consumed a placebo capsule. Each participant received 180 capsules for the trial duration of 3 mo. OUTCOME MEASURES: The primary endpoint was frequency of adverse events; secondary endpoints were changes in physical, vital, blood, and biomarker indices. RESULTS: There were no significant differences in general adverse events or physical, vital, blood, and biomarker indices between the treatment and placebo groups (p > 0.05). However, participants consuming Sutherlandia reported improved appetite compared to those in the placebo group (p = 0.01). Although the treatment group exhibited a lower respiration rate (p < 0.04) and higher platelet count (p = 0.03), MCH (p = 0.01), MCHC (p = 0.02), total protein (p = 0.03), and albumin (p = 0.03), than the placebo group, these differences remained within the normal physiological range, and were not clinically relevant. The Sutherlandia biomarker canavanine was undetectable in participant plasma. CONCLUSION: Consumption of 800 mg/d Sutherlandia leaf powder capsules for 3 mo was tolerated by healthy adults.