Evaluation of the Possible Mechanisms of Antihypertensive Activity of Loranthus micranthus: An African Mistletoe

Phytochemical Analysis and Biological Activities of Ripe Fruits of Mistletoe (Psittacanthus calyculatus)

Psittacanthus calyculatus is a hemiparasitic plant of an arboreal species (e.g., forest, fruit trees). Its foliage has therapeutic potential; however, little is known about its fruits. In this study, the phytochemical profile and biological activities of P. calyculatus fruits hosted by Prosopis laevigata and Quercus deserticola were evaluated. The fruits of P. calyculatus from P. laevigata showed the highest content of total phenols (71.396 ± 0.676 mg GAE/g DW). The highest content of flavonoids and anthocyanins was presented in those from Q. deserticola (14.232 ± 0.772 mg QE/g DW; 2.431 ± 0.020 mg C3GE/g DW). The anthocyanin cyanidin-3-glucoside was detected and quantified via high-performance thin-layer chromatography (HPTLC) (306.682 ± 11.804 mg C3GE/g DW). Acidified extracts from host P. laevigata showed the highest antioxidant activity via ABTS^•+ (2,2'azinobis-(3-ethylbenzothiazdin-6-sulfonic acid) (214.810 ± 0.0802 mg TE/g DW). Fruit extracts with absolute ethanol from the P. laevigata host showed the highest antihypertensive activity (92 ± 3.054% inhibition of an angiotensin converting enzyme (ACE)). Fruit extracts from both hosts showed a minimum inhibitory concentration (MIC) of 6.25 mg/mL and a minimum bactericidal concentration (MBC) of 12.5 mg/mL against Escherichia coli, Salmonella choleraesuis and Shigella flexneri. Interestingly, a significant host effect was found. P. calyculatus fruits extract could be used therapeutically. However, further confirmation experiments should be carried out.

Alpha-cadinol as a potential ACE-inhibitory volatile compound identified from Phaseolus vulgaris L. through in vitro and in silico analysis

Hypertension is a major risk factor of cardiovascular diseases, which is mainly caused due to over activation of renin-angiotensin system. The angiotensin converting enzyme (ACE), which is involved in formation of angiotensin II from angiotensin I, causes the blood vessels to constrict, in turn leading to hypertension. The current study was initiated to understand the role of bioactive volatile compounds from Phaseolus vulgaris L. (common bean), in ACE enzyme inhibition. Beans aqueous extract (BAE) showed maximum ACE inhibition of 88.4 ± 0.8% in comparison to other commonly consumed vegetables like spinach and garlic. The head space gas chromatography-mass spectrometry analysis showed the presence of a number of terpenes and terpenoids, which were present prominently in BAE. In silico molecular docking studies indicated that among the other volatile compounds, alpha-cadinol (-7.27 kcal/mol) and ar-tumerone (-6.44 kcal/mol) have the maximum binding affinity with the active site of ACE, as compared to that of captopril (-6.41 kcal/mol). The molecular dynamic simulation in biological environment, showed that alpha-cadinol forms a stable complex with ACE, with average binding energy of -42 kJ/mol. The ACE:alpha-cadinol complex was found to be stable mainly due to the hydrophobic interactions of alpha-cadinol with active site residues (Tyr523 and Phe457) of ACE. The in silico drug-likeness analysis showed that alpha-cadinol is appropriate for human system with no predicted hepatotoxicity or mutagenicity (AMES toxicity).Communicated by Ramaswamy H. Sarma.

Antunes I, Dömling A, H. Elsinga P. Arginase as a Potential Biomarker of Disease Progression: A Molecular Imaging Perspective

Arginase is a widely known enzyme of the urea cycle that catalyzes the hydrolysis of L-arginine to L-ornithine and urea. The action of arginase goes beyond the boundaries of hepatic ureogenic function, being widespread through most tissues. Two arginase isoforms coexist, the type I (Arg1) predominantly expressed in the liver and the type II (Arg2) expressed throughout extrahepatic tissues. By producing L-ornithine while competing with nitric oxide synthase (NOS) for the same substrate (L-arginine), arginase can influence the endogenous levels of polyamines, proline, and NO•. Several pathophysiological processes may deregulate arginase/NOS balance, disturbing the homeostasis and functionality of the organism. Upregulated arginase expression is associated with several pathological processes that can range from cardiovascular, immune-mediated, and tumorigenic conditions to neurodegenerative disorders. Thus, arginase is a potential biomarker of disease progression and severity and has recently been the subject of research studies regarding the therapeutic efficacy of arginase inhibitors. This review gives a comprehensive overview of the pathophysiological role of arginase and the current state of development of arginase inhibitors, discussing the potential of arginase as a molecular imaging biomarker and stimulating the development of novel specific and high-affinity arginase imaging probes.

In vitro vasodilatory activity and possible mechanisms of the crude extracts and fractions of Moringa stenopetala (Baker f.) Cufod. leaves in isolated thoracic aorta of guinea pigs

Moringa stenopetala, a plant belonging to the family of Moringaceae, is traditionally used for the treatment of hypertension and diabetes in Ethiopia. This study evaluates the in vitro vasodilatory effect of the extract of M. stenopetala leaves and the possible mechanisms in precontracted isolated thoracic aorta of guinea pigs. A guinea pig was sacrificed by gentle cervical dislocation, and the thoracic aortic ring was removed, cut spirally, and mounted in an organ bath containing Krebs-Henseleit physiological solution maintained at 37°C, and then the solution was aerated with carbogen (95% O₂ and 5% CO₂). The vasodilatory activity of cumulative doses of M. stenopetala extracts and fractions was evaluated on intact and denuded endothelium of isolated whole, spirally cut thoracic aortic strips of guinea pigs precontracted with potassium chloride (80 mM), epinephrine (1 μM), methylene blue (10 μM), and glibenclamide (10 μM) using polygraph. All extracts showed a relaxant effect in precontracted isolated whole, spirally cut thoracic aortic strips of guinea pigs in a dose-dependent manner, whereas the greater percentage of relaxant effect was shown with the addition of crude extracts in 80 mM of potassium chloride (99.10% and 95.56% for ethanol and aqueous crude extracts, respectively), and 1 μM of epinephrine (82.85% and 90.16% for ethanol and aqueous crude extracts, respectively) in precontracted isolated whole, spirally cut thoracic aortic strips of guinea pigs. Hence, the possible mechanism of relaxation might be mediated through the blockade of receptor-operated calcium influx and L-type voltage-dependent calcium channels. The aqueous extract showed more significant in vitro vasodilatory effect than its fractions and 70% ethanol extract.

Loranthus ferrugineus: a Mistletoe from Traditional Uses to Laboratory Bench

Objectives:

Loranthus ferrugineus (L. ferrugineus) from Loranthaceae, a mistletoe, is a medicinal herb used for a variety of human ailments. Traditionally, decoctions of this parasitic shrub have been mainly used to treat high blood pressure (BP) and gastrointestinal complaints; usage which is supported by experimental based pharmacological investigations. Nonetheless, there is still limited data available evaluating this plant’s traditions, and few studies have been scientifically translated toward evidence based phytomedicine. We therefore provide a concise review of the currently available L. ferrugineus literature and discuss potential directions for future areas of investigation.

Methods:

We surveyed available literature covering ethnopharmacological usage of L. ferrugineus and discussed relevant findings, including important future directions and shortcomings for the medicinal values of this parasitic shrub.

Results:

Evidence based pharmacological approaches significantly covered the medicinal application of L. ferrugineus for hypertension and gastrointestinal complaint management, with a particular focus on the active hydrophilic extract of this herb.

Conclusion:

Understanding the sites of action of this plant and its beneficial effects will provide justification for its use in old traditional treatments, and potentially lead to the development of therapies. Other medicinal applicative areas of this parasitic shrub, such as wound healing, gerontological effects, and antiviral and anticancer activities, are yet to be researched.

Loranthus micranthus Linn.: Biological Activities and Phytochemistry

Loranthus micranthus Linn. is a medicinal plant from the Loranthaceae family commonly known as an eastern Nigeria species of the African mistletoe and is widely used in folkloric medicine to cure various ailments and diseases. It is semiparasitic plant because of growing on various host trees and shrubs and absorbing mineral nutrition and water from respective host. Hence, the phytochemicals and biological activities of L. micranthus demonstrated strong host and harvesting period dependency. The leaves have been proved to possess immunomodulatory, antidiabetic, antimicrobial, antihypertensive, antioxidant, antidiarrhoeal, and hypolipidemic activities. This review summarizes the information and findings concerning the current knowledge on the biological activities, pharmacological properties, toxicity, and chemical constituents of Loranthus micranthus.