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Abstract: The polyphenols (CPAE II) was isolated from the dichloromethane extract of the pyroligneous acid, Rhizophora apiculata by simultaneous acid base and solvent extraction method. Its qualitative and quantitative composition was studied by gas chromatography mass spectroscopy (GC/MS) and out of 57 peaks, 52 compounds were identified, representing 95.47% of the total polyphenols. The CPAE II was then fractionated to four fractions (F1–F4) by means of thin layer chromatography and silica gel column chromatography with dichloromethane, dichloromethane/chloroform/ethyl acetate mixture (8:1:1; 4:3:3, v/v/v), and ethyl acetate, respectively. The antioxidant properties of the CPAE II and the fractions were evaluated. Among the four fractions, fraction 1 (F1) was the most potent in DPPH radical scavenging activity and molybdenum (VI) reducing power. It was subjected to further purification by means of silica gel column chromatography with hexane, hexane/diethyl ether mixture (9:1, 6:1, 3:1, v/v), and diethyl ether, respectively. 2,6-Dimethoxyphenol (syringol) and dihydroxybenzenes (catechol and 3-methoxycatechol) were isolated and identified by GC/MS, 1H NMR, 13C NMR spectral analyses, and confirmed by GC co-injection with authentic standards. Syringol, catechol and 3-methoxycatechol constitute 39.08, 4.21 and 1.10% of F1, respectively. Their antioxidant activities were evaluated by DPPH radical scavenging activity, ABTS radical cation scavenging activity, phosphomolybdenum and ferric reducing antioxidant power (FRAP). The trend in antioxidant capacity was similar in all the four assays, with dihydroxybenzenes > 2,6-dimethoxyphenols, although discrepancies in the ranking within the dihydroxybenzenes were present. These three compounds which showed significant antioxidant activities were isolated for the first time from the pyroligneous acid, R. apiculata. [Copyright &y& Elsevier]

Abstract: Depolymerisation of mangrove Rhizophora apiculata bark extracts in the presence of phloroglucinol nucleophiles in ethanol was carried out. The flavan-3-ols and their phloroglucinol adducts were separated using reversed phase liquid chromatography (HPLC). The HPLC analysis of mangrove R. apiculata showed that catechin was the most common component of the flavanoid monomers. The antioxidant activities of these mangrove tannins were evaluated and compared with several commercial tannins by using reducing power, DPPH and ABTS assays with butylated hydroxytoluene, BHT and l-(+)-ascorbic acid as standards. All tannins had reducing power and percentage scavenging activities similar to the (+)-catechin and l-(+)-ascorbic acid standards. In the DPPH assay, >90% of the maximum scavenging activity was attained at 30μgml−1. Mangrove tannins had stronger antioxidant activity than the BHT standard in the DPPH assay. The results of the ABTS assay were correlated with the DPPH assay. Scavenging activity in the ABTS assay increased as the tannin concentration increased, up to a plateau at 50μgml−1. [Copyright &y& Elsevier]

Abstract: Total phenolics content, free radical scavenging activity, reducing power, and antioxidant activity of the pyroligenous acid from a mangrove plant, Rhizophora apiculata were evaluated. Dichloromethane extraction of the raw pyroligneous acid successfully yield 2 extracts, i.e. concentrated pyroligneous acid (CPA) and concentrated pyroligneous acid extract (CPAE). Phenolic contents in CPAE and CPA, expressed as (±)-catechin equivalents/g of the sample were 5465±367 mg and 2502±152mg, and expressed as gallic acid equivalents/g of the sample were 2919±209mg and 1348±90mg, respectively. CPAE exhibited superior free radical scavenging activity with EC50 value=0.1235mg/ml, or 80.96% of free radical scavenging capability. The ferric reducing power of CPAE was approximately 3.7, 5.1, 6.1, and 21.3 times higher than that of ascorbic acid, BHA, BHT and alpha-tocopherol. In phosphomolybdenum assay, CPAE showed the greatest antioxidant efficacy (A 695 =1.278) compared to those of CPA and different standards. In addition, the free radical scavenging activity, ferric reducing power and total antioxidative activity of CPAE and CPA showed positive correlation with their total phenolic content with R 2 values ranging from 0.9624 to 0.9979. [Copyright &y& Elsevier]