In-silico and in-vitro screening of Asiatic acid and Asiaticoside A against Cathepsin S enzyme.

BACKGROUND: Atherosclerosis is a form of cardiovascular disease that affects the endothelium of the blood vessel. Series of events are involved in the pathophysiology of this disease which includes the breaking down of the connective tissue elastin and collagen responsible for the tensile strength of the arterial wall by proteolytic enzyme. One of these enzymes called Cathepsin S (CatS) is upregulated in the progression of the disease and its inhibition has been proposed to be a promising pharmacological target to improve the prognosis of the disease condition. Asiatic acid and asiaticoside A are both pentacyclic triterpenoids isolated from Centella asiatica. Their use in treating various cardiovascular diseases has been reported. METHODS: In this study through in silico and in vitro methods, the pharmacokinetic properties, residue interaction, and inhibitory activities of these compounds were checked against the CatS enzyme. The SwissADME online package and the ToxTree 3.01 version of the offline software were used to determine the physicochemical properties of the compounds. RESULT: Asiatic acid reported no violation of the Lipinski rule while asiaticoside A violated the rule with regards to its molecular structure and size. The molecular docking was done using Molecular Operating Environment (MOE) and the S-score of - 7.25988, - 7.08466, and - 4.147913 Kcal/mol were recorded for LY300328, asiaticoside A, and asiatic acid respectively. Asiaticoside A has a docking score value (- 7.08466Kcal/mol) close to the co-crystallize compound. Apart from the close docking score, the amino acid residue glycine69 and asparagine163 both interact with the co-crystallized compound and asiaticoside A. The in vitro result clearly shows the inhibitory effect of asiaticoside and asiatic acid. Asiaticoside A has an inhibitory value of about 40% and asiatic acid has an inhibitory value of about 20%. CONCLUSION: This clearly shows that asiaticoside will be a better drug candidate than asiatic acid in inhibiting the CatS enzyme for the purpose of improving the outcome of atherosclerosis. However, certain modifications need to be made to the structural make-up of asiaticoside A to improve its pharmacokinetics properties.

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.

The contributions of muscarinic receptors and changes in plasma aldosterone levels to the anti-hypertensive effect of Tulbaghia violacea.

BACKGROUND: Tulbaghia violacea Harv. (Alliaceae) is used to treat various ailments, including hypertension (HTN) in South Africa. This study aims to evaluate the contributions of muscarinic receptors and changes in plasma aldosterone levels to its anti-hypertensive effect. METHODS: In the acute experiments, methanol leaf extracts (MLE) of T. violacea (30-120 mg/kg), muscarine (0.16 -10 µg/kg), and atropine (0.02 - 20.48 mg/kg), and/or the vehicle (dimethylsulfoxide (DMSO) and normal saline (NS)) were respectively and randomly administered intravenously in a group of spontaneously hypertensive (SHR) weighing 300 to 350 g and aged less than 5 months. Subsequently, T. violacea (60 mg/kg) or muscarine (2.5 µg/kg) was infused into eight SHRs, 20 min after atropine (5.12 mg/kg) pre-treatment. In the chronic (21 days) experiments, the SHRs were randomly divided into three groups, and given the vehicle (0.2 ml/day of DMSO and NS), T. violacea (60 mg/kg/day) and captopril (10 mg/kg/day) respectively into the peritoneum, to investigate their effects on blood pressure (BP), heart rate (HR), and plasma aldosterone levels. Systolic BP and HR were measured using tail-cuff plethysmography during the intervention. BP and HR were measured via a pressure transducer connecting the femoral artery and the Powerlab at the end of each intervention in the acute experiment; and on day 22 in the chronic experiment. RESULTS: In the acute experiments, T. violacea, muscarine, and atropine significantly (p < 0.05) reduced BP dose-dependently. T. violacea and muscarine produced dose-dependent decreases in HR, while the effect of atropine on HR varied. After atropine pre-treatment, dose-dependent increases in BP and HR were observed with T. violacea; while the BP and HR effects of muscarine were nullified. In the chronic experiments, the T. violacea-treated and captropril-treated groups had signicantly lower levels of aldosterone in plasma when compared to vehicle-treated group. Compared to the vehicle-treated group, significant reduction in BP was only seen in the captopril-treated group; while no difference in HR was observed among the groups. CONCLUSION: The results obtained in this study suggest that stimulation of the muscarinic receptors and a reduction in plasma aldosterone levels contribute to the anti-hypertesive effect of T. violacea.

Effect of Tulbaghia violacea on the blood pressure and heart rate in male spontaneously hypertensive Wistar rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Tulbaghia violacea Harv. (Alliaceae) is a small bulbous herb which belongs to the family Alliaceae, most commonly associated with onions and garlic. In South Africa, this herb has been traditionally used in the treatment of various ailments, including fever, colds, asthma, paralysis, hypertension and stomach problems. The aim of this study was to evaluate the effect of methanol leaf extracts (MLE) of Tulbaghia violacea on the blood pressure (BP) and heart rate (HR) in anaesthetized male spontaneously hypertensive rats; and to find out the mechanism(s) by which it acts. MATERIALS AND METHODS: The MLE of Tulbaghia violacea (5-150mg/kg), angiotensin I human acetate salt hydrate (ang I, 3.1-100µg/kg), angiotensin II human (ang II, 3.1-50µg/kg), phenylephrine hydrochloride (phenylephrine, 0.01-0.16mg/kg) and dobutamine hydrochloride (dobutamine, 0.2-10.0µg/kg) were infused intravenously, while the BP and HR were measured via a pressure transducer connecting the femoral artery and the Powerlab. RESULTS: Tulbaghia violacea significantly (p<0.01) reduced the systolic, diastolic, and mean arterial BP; and HR dose-dependently. Ang I, ang II, phenylephrine and dobutamine all increased the BP dose-dependently. The hypertensive effect of ang I and the HR-increasing effect of dobutamine were significantly (p<0.01) decreased by their co-infusion with Tulbaghia violacea (60mg/kg). However, the co-infusion of ang II or phenylephrine with Tulbaghia violacea (60mg/kg) did not produce any significant change in BP or HR when compared to the infusion of either agent alone in the same animal. CONCLUSIONS: Tulbaghia violacea reduced BP and HR in the SHR. The reduction in BP may be due to actions of the MLE on the ang I converting enzyme (ACE) and ß(1) adrenoceptors.