Effect of Acacia catechu (L.f.) Willd. on Oxidative Stress with Possible Implications in Alleviating Selected Cognitive Disorders

Abstract

In human body, several categories of degenerative processes are largely determined by free radicals originating in cell. Free radicals are also known to have correlated with a variety of cognitive disorders (CDs) resulting in neuronal injury and eventually to death. Alzheimer's disease (AD) and Parkinson's disease (PD) are such kind of killer CDs that occur due to dysfunction of cholinergic and dopaminergic neurons. Plant parts of Ginkgo biloba, Bacopa monnieri etc. are being used for the treatment of cognitive disorders in several countries. The present study was aimed to explore the detailed antioxidant and anti-cholinesterase activity of Acaciacatechu leaf (ACL) over CDs. Gas chromatography-Mass spectroscopy (GC-MS) analysis and Nuclear Magnetic Resonance (NMR) were employed to identify the bioactive components present in ACL. Furthermore, the extract was evaluated to check the cytotoxic effects of ACL on normal cells. Amongst several antioxidant assays, DPPH assay, hydroxyl radical, nitric oxide radical and hypochlorous acid inhibitory activities were found to be greater in ACL than that of the respective standards while other assays exhibited a moderate or at per inhibitory activity with standards. Total phenolic and flavonoid content were also found to be present in decent amount. In addition, we found, a greater acetylcholinesterase (AChE) inhibitory activity of ACL when compared to other medicinally important plants, indicating its positive effect over CDs. Forty one bioactive components were explored through GC-MS. Of these, gallic acid, epicatechin, catechin, isoquercitrin etc. were found, which are potent antioxidant and a few of them have anti-neurodegenerative properties. Eventually, ACL was found to be nontoxic and safer to consume. Further studies with animal or human model however, would determine its efficacy as a potential anti-schizophrenic drug.

Fig 1. Antioxidant and free-radical scavenging activities of ACL extract.

(A) DPPH radical scavenging activities of ACL extract and standard ascorbic acid (IC₅₀ value: ACL = 15.52±0.46μg/ml and ascorbic acid = 240.10±28.35 μg/ml; p<0.001). (B) Total reductive abilities of ACL extract and standard butylated hydroxytoluene (BHT). The absorbance (A₇₀₀) was plotted against concentration of sample; higher absorbance value signified greater reducing capacity. (C) Hydroxyl radical scavenging capacities of ACL extract and standard mannitol (IC₅₀ value: ACL = 121.20±1.22μg/ml and mannitol = 589.06±46.57μg/ml; p<0.01). (D) Superoxide radical scavenging activities of ACL extract and standard quercetin (IC₅₀ value: ACL = 131.900±4.40μg/ml and quercetin = 63.93±4.16μg/ml; p<0.01). [Each value represents mean ±SD (n = 6); Where, α = p<0.001 Vs 0 μg/ml].

Fig 2. Free-radical scavenging potentials of ACL extract.

(A) Singlet oxygen scavenging capacities of ACL extract and standard lipoic acid (IC₅₀ value: ACL = 1103.79±24.69μg/ml and lipoic acid = 48.40±2.02μg/ml; p<0.001). (B) Nitric oxide (NO) scavenging activities of ACL extract and standard Curcumin (IC₅₀ value: ACL = 45.57±1.33μg/ml and curcumin = 96.88±5.09μg/ml; p<0.01). (C) Peroxynitrite scavenging activities of ACL extract and standard gallic acid (IC₅₀ value: ACL = 854.05±59.96 μg/ml and gallic acid = 734.81±28.30 μg/ml; p>0.05). (D) Hypochlorous acid (HOCL) scavenging activities of ACL extract and standard ascorbic acid (IC₅₀ value: ACL = 130.675±4.78 μg/ml and ascorbic acid = 165.91±16.31μg/ml; p<0.01). [Each value represents mean ±SD (n = 6); Where, α = p<0.001 Vs 0 μg/ml].

Fig 3. Iron (Fe²⁺)-chelation activities of ACL extract and the reference compound.

(A) ACL extract and (B) standard Ethylenediaminetetraacetic acid (EDTA), represented as % of Fe²⁺-ferrozine complex (IC₅₀ value: ACL = 320.63±10.82μg/ml and EDTA = 1.45±0.01μg/ml; p<0.001). [Each value represents mean ±SD (n = 6); Where, α = p<0.001 Vs 0 μg/ml].

Fig 4. Hydrogen peroxide scavenging and lipid peroxidation inhibitory activity of ACL extract and the reference compound.

(A) Hydrogen peroxide (H₂O₂) scavenging activities of ACL extract and standard sodium pyruvate (IC₅₀ value: ACL = 15604.93±613.81μg/ml and sodium pyruvate = 3176.40±140.22μg/ml; p<0.001). (B) Inhibition of lipid peroxidation by ACL extract and standard trolox (IC₅₀ value: ACL = 32.13±0.99μg/ml and trolox = 11.11±0.22μg/ml; p<0.001). [Each value represents mean ±SD (n = 6); Where, α = p<0.001, β = p<0.01 and γ = p<0.05 Vs 0 μg/ml.].

Fig 5. Gas chromatogram-Mass spectroscopy of A. catechu leaf extract.

Fig 6. Chemical structures of some essential bioactive metabolites identified in ACL extract by GC-MS.

Fig 7. Schematic representation of possible biosynthetic pathway of catecholamines identified in ACL extract.

Fig 8. (A) ¹³C NMR spectra and (B) ¹H NMR spectra of ACL extract.

Fig 9. The effect of ACL extract on the viability of murine splenocytes and peritonealexudate macrophages, evaluated by MTT method.

Each value represents mean ±SD (n = 6); Where, ^NSp = 0>0.05.