STUDIES ON CHEMICAL CONSTITUENTS AND BIOLOGICAL ACTIVITIES OF CONOCARPUS LANCIFOLIUS (COMBRETACEAE)

Abstract

The research work was carried out for the phytochemical and biological studies of Conocarpus lancifolius (Combretaceae). Collected plant material was subjected for preliminary phytochemical screening and revealed the presence of cardiac glycosides, saponins, flavonoids, and tannins while alkaloids were absent. Dichloromethane and methanol extracts were prepared and screened for antibacterial activity, antifungal activity, brine-shrimp toxicity, phytotoxicity, antioxidant activity, α-chymotrypsin inhibitory activity, urease inhibitory activity, α-glucosidase inhibitory activity and butyrylcholinesterase inhibitory activity. Dichloromethane extract of Conocarpus lancifolius exhibited moderate antioxidant activity with a percentage inhibition of 42.06±0.64 mg/ml, while the percentage inhibition of methanol extract by DPPH method was 92.1± 0.1 with 396.205 IC50 value, percentage inhibition by nitric oxide scavenging activity was 93.35± 0.61 and percentage inhibition by ferric reducing antioxidant power method was 93.2± 1.02. Dichloromethane extract of Conocarpus lancifolius showed significant α- chymotrypsin inhibition activity with percentage inhibition of 92.20 ± 1.82 and 91.17 ± 0.82 μg/ml IC50 value. Both the extracts of Conocarpus lancifolius exhibited significant lipoxygenase inhibition activity with percentage inhibition of 65.97 ± 0.55 and 63.89 ± 0.02 with IC50 value 158.61 ± 0.08 and 186.31±0.04 respectively. Methanol extract of Conocarpus lancifolius showed significant acetylcholinesterase inhibition activity with percentage inhibition of 87.48 ± 0.09 with 71.21 ± 0.11 IC50 value. Dichloromethane and methanol extracts of Conocarpus lancifolius have promising butyrylcholinesterase inhibition activity with percentage inhibition of 89.52±0.39 at 0.5 mg/ml and 89.06±0.89 with IC50 values 55.25±0.07 and 52.31± 0.11 respectively. Methanol extract of Conocarpus lancifolius was found toxic with LD50 value of 115.76 (0.0048 - 13.76) μg/ml against Artemia salina. Methanol extract of Conocarpus lancifolius exhibited a significant antiurease activity having percentage inhibition value 81.1±1.82 with 49.1± 1.31 IC50 value. Dichloromethane extract of Conocarpus lancifolius showed carbonic anhydrase inhibition activity with 56.7 2.44 IC50 values using acetazolamide as standard. The aqueous ethanol extracts of Conocarpus lancifolius relaxed the spontaneous contractions in isolated rabbit jejunum preparations in dose dependant manner at 0.01- 3 mg/ml tissue bath concentrations. However aqueous ethanol extract of Conocarpus lancifolius relaxed K+ (80 mM) induced contractions in isolated rabbit jejunum 3 preparation and also relaxed carbachol (1μM) induced contraction in isolated rabbit tracheal preparations in dose dependant manner (0.1-3 mg/ml). It is to be reported that the observed response is likely to be mediated through either anti muscuranic activity or/ and blockade of voltage dependant Ca+2 channels. The aqueous ethanol extract of roots of Conocarpus lancifolius have shown a significant relaxant effect in isolated rabbit jejunum preparations with an EC50 value of 0.2075 mg/ml (95% CI: 0.0478- 0.9007). Methanol extract of Conocarpus lancifolius showed a significant α-glucosidase inhibitory activity with an inhibition (%) value of 79.56 and 5.59±0.06μg/ml IC50 value at even very low concentration of 0.0039 mg/ml. Acarbose which exhibit 92.23 % inhibition and 38.25 μg/ml IC50 value was used as standard. On the basis of in vitro α-glucosidase inhibitory activity in vivo study was also carried out on rabbits. Methanol extract of Conocarpus lancifolius significantly decreases the blood glucose level in alloxan induced diabetic rabbits. The pharmaceutical industry is facing serious challenges for drug discovery process. The available drugs for various diseases are extremely expensive, riskier, and critically inefficient. Keeping in view these facts isolation of compounds from dichloromethane and methanol extracts was carried out and seven compounds Quercetin 3-O-glucuronide (A), S-4-isopropyl-8-methoxy-6-thia-bicyclo[3.2.1]oct-1- en-2-yl benzothioate (B), 2,3,4,8,9,10,11,13-octahydro-1H-phenanthro[3,2-c]oxocin- 3-yl benzoatem (C), 1,3,4,5,6,8-hexahydroxy-3,4,5,5a-tetrahydro-1H-benzo[g] isochromene-5-carboxylic acid (D),1-amino-1,5,7,8-tetramethoxy-1Hcyclopenta[ a]naphthalene-2-carboxamide (E), 2,3,8 tri-O-methyl ellagic acid (F), 3- O-methyl ellagic acid 4-O- β -D glucopyranoside (G) were isolated. The chemical structures of isolated compounds (A-G) were established with the help of spectroscopic techniques such as ultraviolet-visible, infrared, proton nuclear magnetic resonance (1H-NMR), 13C NMR (BB, DEPT-135, 90), two dimensional correlation techniques (COSY, HSQC) and mass spectrometry. All compounds were isolated first time from genus conocarpus. The compounds S-4- isopropyl-8-methoxy-6-thia-bicyclo[3.2.1]oct-1-en-2-yl benzothioate (B), 2,3,4,8,9,10,11,13-octahydro-1H-phenanthro[3,2-c]oxocin-3-yl benzoate (C) and 1-amino-1,5,7,8-tetramethoxy-1H-cyclopenta[a]naphthalene-2-carboxamide (E) not only isolated for the first time from genus conocarpus but have noval structures. The S-4-isopropyl-8-methoxy-6-thia-bicyclo[3.2.1]oct-1-en-2-yl benzothioate compound 4 (B) was subjected to antimicrobial activity test against the clinical microbes to determine its biological activities. The zone of inhibition was observed to be between 20 to 24 mm with Bacillus Subtilis having the largest zone of inhibition of 24 ml. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) was determined. It was found that the MFC was higher than that of standard drug Fluconazole. All compounds were screened for antioxidant, in vitro α- glucosidase inhibitory activity, acetylchohline esterase inhibitory activity, and butyl cholinesterase and urease inhibitory activity. F and G compound showed antioxidant activity which is significant when calculated by DPPH method having percentage inhibition of 83.68±0.18 and 68.43±0.17 at 0.5 mM. A, B, C, D and E compounds represented a moderate antioxidant activity by DPPH method having percentage inhibition 42.14±0.13, 16.23±0.15, 16.55±0.13, 17.15±0.16 and 13.36±0.17. Acetylchohline esterase inhibitory activity of compound C and D has significant values 71.62±0.16 and 65.91±0.17. Compounds A-G has exhibited a little percentage inhibition activity of butyl cholinesterase. C, F and G compounds have significant α- glucosidase inhibition with percentage inhibition of 92.83±0.18, 72.26±0.18 and 92.58±0.2. B compound showed a little percentage inhibition of 64.25±0.24. A, D and E compounds have little activity with percent inhibitory values of 17.74±0.17, 42.24±0.16 and 32.64±0.14. Acarbose was taken as standard drug. G compound has shown significant urease inhibitory activity with percentage inhibition 66.54±0.26. A, B, C, D, E and F compounds have little percentage inhibition of 45.91±0.15, 48.85±0.16, 39.75±0.14, 35.96±0.15, 38.64±0.12 and 40.79±0.14m respectively.