Preliminary investigation of acaricidal activity of leaf extract of Nicotiana tabacum on dog tick Rhipicephalus sanguineus

BACKGROUND AND AIM

Tick infestation of domestic animals remains a major constraint to livestock productivity across all agro-ecological zones most especially in small animal practice. The most common method of tick control is the use of synthetic acaricide. However, a widespread increase of acaricidal resistance, scarcity and high cost of acaricides especially to farmers of low-income earnings in developing countries support the need for alternative tick control methods. Among the alternative methods for tick control is herbal therapy. In this study, we investigated the acaricidal activity of methanol and N-hexane leaf extracts of Nicotiana tabacum against dog ticks - Rhipicephalus sanguineus.

MATERIALS AND METHODS

Larvicidal and adulticidal activity of N. tabacum leaf extract were examined on the dog tick - R. sanguineus in an in vitro experiment using larval packet test and adult immersion test respectively. Phytochemical and Gas Chromatography-Mass Spectrometry (GC-MS) analysis of the leaf extract were also carried out using standard methods.

RESULTS

We observed a tick mortality rate that was concentration-dependent. However, N-hexane extract showed a higher significant acaricidal effect than methanol extract. Lethal dose (LD50) of N. tabacum was 0.06. High quantity of terpenoids was obtained from N. tabacum. Lower tick glutathione S-transferase observed with varying concentration of N. tabacum. GC-MS revealed Pyridine, 3-(1-methyl-2-pyrrolidinyl)-, (S) - Nicotine, Citronellyl propionate, Crotonaldehyde, Lavandulyl acetate, trans-Phytol and Amitrole (3-Amino-1, 2, 4-triazole) in N. tabacum.

CONCLUSION

Both methanol and N-hexane leaf extracts of N. tabacum exhibited observable acaricidal property against the larvae and adult R. sanguineus of dog.

Ameliorative effects of Annona muricata Linn. (Annonaceae) against potassium dichromate-induced hypertension in vivo: involvement of Kim-1/p38 MAPK/Nrf2 signaling

Background Recently, the incidences of hypertension and environmental pollution have increased significantly. This study investigates the antihypertensive effect of Annona muricata extract against K2Cr2O7-induced hypertension. Methods Fifty rats were used for this study, which were divided into five groups of 10 rats each. Rats in Group A received normal saline, and those in Groups B, C, D, and E were treated with A. muricata extract alone at 250 mg/kg, K2Cr2O7 at 30 mg/kg, pretreated with the extract at 250 mg/kg, and pretreated with gallic acid at 60 mg/kg for 14 days, respectively, and thereafter administered with a single intraperitoneal injection of K2Cr2O7 at 30 mg/kg. Results Administration of K2Cr2O7 significantly increased systolic, diastolic, and mean arterial pressure and caused prolonged QT and QTc intervals. Further, pretreatment with the extract at 250 mg/kg and gallic acid at 60 mg/kg significantly reduced high blood pressure to near-normal values. K2Cr2O7 intoxication led to significant increases in serum advanced oxidative protein products, myeloperoxidase, and xanthine oxidase, while serum nitric oxide (NO) also reduced significantly. Immunohistochemistry of the renal kidney injury molecule (Kim-1) and p38 MAPK showed increased expressions following the administration of K2Cr2O7 together with the downregulation of nuclear factor erythroid 2-related factor 2 (Nrf2). Pretreatment with the extract at 250 mg/kg and gallic acid at 60 mg/kg also increased the expressions of Nrf2 and downregulated Kim-1 and p38. Conclusion Together, we found that pretreatment with the extract at 250 mg/kg and gallic acid at 60 mg/kg normalized the blood pressure, reduced the markers of oxidative stress, and improved the antioxidant defense system and serum NO bioavailability.

Antihypertensive Effect of Polyphenol-Rich Fraction of Azadirachta indica on Nω-Nitro-L-Arginine Methyl Ester-Induced Hypertension and Cardiorenal Dysfunction

Azadirachta indica (AI) is a medicinal plant with reported antioxidant and cardio-protective properties. The use of plant-based polyphenols has become greatly increased in the last one decade. The present study investigated the protective effect of the polyphenol-rich fraction (PRF) of the methanol-extract of Azadirachta indica against N^ω-Nitro-L-Arginine Methyl Ester (L-NAME) induced hypertension and cardiorenal dysfunction in rats. Fifty (50) Wistar albino rats were grouped into five groups. Group A, the control, was administered potable water. Groups B-E received orally, 40 mg/kg of L-NAME only, 40 mg/kg of L-NAME and 100 mg/kg of AI extract, 40 mg/kg of L-NAME and 200 mg/kg of AI extract, and 40 mg/kg of L-NAME and 25 mg/kg of captopril, respectively for 21 days. The results of the present study revealed that L-NAME administration led to a significant increase in systolic blood pressure, diastolic blood pressure, and mean arterial blood pressure. Markers of oxidative stress (malondialdehyde,protein carbonyl) increased significantly while there was reduction in reduced glutathione level, activities of superoxide dismutase, glutathione peroxidase and glutathione-S-transferase as well nitric oxide bioavailability. Immunohistochemistry revealed higher expressions of nuclear factor kappa beta (NF-kB) and kidney injury molecule 1(Kim-1) and lower expressions of nuclear factor erythroid 2-related factor 2 (Nrf2) in hypertensive rats. Our results indicated that with PRF of AI restored high blood pressure, reduced markers of oxidative stress, normalized serum NO bioavailability and increased the expressions of Nrf2. Hence, PRF of Azadirachta indica could be used for the treatment of hypertension.

Chemical Composition and Antibacterial Activity of Essential Oil of Cosmos bipinnatus Cav. Leaves from South Africa

The chemical composition of essential oils isolated from the leaves of Cosmos bipinnatus and its antibacterial activity were analyzed by GC-MS and microbroth dilution assay respectively. The essential oil extracted from this plant was predominantly composed of monoterpenes (69.62%) and sesquiterpenes (22.73%). The antibacterial assay showed that the oil had significant inhibitory effects against both Gram-negative and Gram-positive bacteria isolates. The MIC of Gram-positive strains ranged between 0.16 and 0.31 mg/mL while those of Gram-negative bacteria ranged between 0.31 and 0.63 mg/mL. The Gram-positive bacteria were more susceptible to the essential oil than the Gram-negative bacteria. Most of the major components of this oil in other plants have been reported for antimicrobial activities. The antibacterial activity can be attributed to effects of the combination of several components of the oil. The results indicate that the C. bipinnatus might be exploited as natural antibacterial agent and have application in the treatment of several infectious diseases caused by these bacteria. Since this species is endemic to the eastern Free State, the plant could be collected during its bloom and used efficiently in the management of bacterial infections in South Africa.