Appraisal of Ajuga bracteosa Wall. ex Benth. as a promising natural source of bioactive leads

Abstract

The traditional plants occupy fundamental place for the fulfillment of healthcare needs in developing countries. The current study was aimed to purify and characterize bioactive leads from a medicinal folklore, Ajuga bracteosa Wall. ex Benth. Initially, total fifteen extracts were prepared from dried powdered plant material in different solvent systems using ultra sonication aided maceration. These extracts were evaluated to reconnoiter phytochemical and biological (i.e., antioxidant, antimicrobial, cytotoxic and enzyme inhibitory) attributes. Existence of huge amounts of polyphenols was confirmed in methanol extract (via RP-HPLC analysis) along with highly promising antioxidant and protein kinase inhibitory activities and moderate α-amylase inhibitory, antileishmanial and cytotoxic potential. Therefore, methanol was selected as the most suitable solvent for bulk extraction. Afterwards, the preparative extract (ABCM) was partitioned through solvent-solvent extraction and the resultant main fractions (i.e., ABH, ABE and ABW) were processed through various chromatographic procedures by simultaneously gauging their activities against antioxidant, enzyme inhibitory and cytotoxic assays. AB1 was isolated from its ABH fraction with prominent α-amylase inhibitory activity (IC50 119.4±0.22 µg/ml). AB2, AB3, AB4 and AB5 were isolated from ABE fraction. AB2 gave moderate protein kinase inhibitory potential (i.e., 7.67±0.58 mm bald zone of inhibition). AB3 and AB4 manifested good cytotoxic potential (with LC50 111.52±0.24 and 78.56±0.53 µg/ml respectively) while AB4 also showed good free radical scavenging (with IC50 10.4±0.32 µg/ml) and α-amylase inhibitory potential (with IC50 134±0.56 µg/ml). Magnificent total antioxidant and reducing activities (i.e., 182.8±0.72 and 760.12±0.64 µg AAE/mg compound respectively) were shown by AB5. The ABW fraction resulted in AB6 with moderate cytotoxic potential (with LC50 183.42±0.57 µg/ml). X-ray crystallographic and spectroscopic studies characterized AB1, AB2, AB3, AB4, AB5 and AB6 as 2, 3dihydroxy propyl palmitate, ajugarin I, apigenin, luteolin, ajugarin VI and 8-Oacetylharpagide respectively. In vivo activities including antiinflammatory, analgesic, antidepressant and anticoagulant were designed for further confirmation of the above said activities at compound level. The results revealed high dose (HD, 20 mg/kg) of AB2, AB3 and AB6 to be potent antiinflammatory agents with values ranging between 70-90% edema inhibitions. AB1, AB2 and AB6 showed excellent analgesic behavior with > 90% increment in pain threshold whereas HD and LD (low dose, 10 mg/kg) of AB2 showed maximum antidepressant activity in the range of 90-100 seconds. The remarkable anticoagulant profile (with 143±4.77 seconds for blood coagulation) was shown by HD of AB6. On the basis of previous hepatoprotective reports from the subject plant, the most abundant compound, AB2 was selected for confirmation of hepatoprotective and renoprotective aspects using in vivo CCl4 toxicity model. Endogenous antioxidants i.e. superoxide dismutase, catalase, peroxidase, glutathioneS-transferase and reduced glutathione were revitalized with HD (4 mg/kg) of AB2 exhibiting the activity levels of 4.54±0.39, 4.22±0.41 and 9.02±0.79 U/min, 18.97±1.79 nM/min/mg protein and 20.3±1.7 nM/mg protein respectively. Reduced serum levels of hepatic as well as renal markers i.e. alanine transaminase, aspartate transaminase, alkaline phosphatase (with 43.7±0.21, 37.2±0.13 and 201.3±0.029 U/l respectively), urea and creatinine (with 24.07±0.19 and 0.98±0.11 mg/dl respectively) were observed with HD of AB2. The lipid profile also showed ameliorative effects for serum triglycerides and cholesterol (i.e., 104±0.34 and 147.2±0.03 mg/dl respectively) at HD. Abnormalities in histoarchitecture of both the organs were curbed by HD of the compound indicating its regenerative properties. In principle, the aforementioned findings endorses A. bracteosa as a substantial source of bioactive leads with marvelous pharmacological spectrum.