Effect of Extraction Techniques on Phenolic Content, Antioxidant and Antimicrobial Activity of Bauhinia purpurea : HPTLC
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Effect of Extraction Techniques on Phenolic Content, Antioxidant and Antimicrobial Activity of Bauhinia purpurea: HPTLC Determination of Antioxidants H. V. Annegowda & M. N. Mordi & S. Ramanathan & M. R. Hamdan & S. M. Mansor
Received: 16 January 2011 / Accepted: 7 March 2011 / Published online: 2 April 2011 # Springer Science+Business Media, LLC 2011
Abstract Bauhinia purpurea leaf was extracted by Soxhlet, ultrasonication and maceration extraction methods using ethanol (99.5%, v/v) to obtain Soxhlet (SBE), ultrasonicated (UBE) and macerated (MBE) B. purpurea leaf extract. The effects of different extracting methods on the polyphenolic content and antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azinobis (3-ethylbenzothiazoline-6sulfonic acid) diammonium salt (ABTS), ferric-reducing antioxidant power (FRAP) and total antioxidant capacity (TAC) were investigated. Disc diffusion and broth dilution methods were also carried out to find the antibacterial activity of these extracts. Findings of this study showed that UBE possessed significant (PMBE (8.3). This higher yield of Soxhlet extraction might be because of its exhaustive extraction ability. Total phenolic content of SBE, UBE and MBE were 117.0±0.7, 196.8±0.4 and 130.4±1.6 mg GAE/g extract, respectively (Table 1). Our results showed that 1 h of sonication extracted out a significant amount of phenolic content (PSBE. Figure 2 shows the ABTS radical scavenging activity of SBE, UBE, MBE, vitamin C and BHT. Almost a similar trend of DPPH assay was observed here; the plateau was achieved at a concentration of 20 μg/ mL for UBE (98.7±0.5) and vitamin C (98.4±2.2), whereas
Fig. 2 ABTS radical scavenging activity of different extracts and standards
at a concentration of 40 μg/mL macerated extract, BHT and Soxhlet showed percentage inhibition of 88.6±3.0, 83.5±2.1 and 71.4±0.9, respectively. At all the concentrations evaluated, UBE possessed the highest ABTS radical scavenging activity in comparison with other extracts and standard samples. Total Antioxidant Capacity and Ferric-Reducing Antioxidant Potency Assays Antioxidants present in the sample which caused the reduction of Mo(VI) to Mo(V) result in the formation of green phosphomolybdenum complex which was measured
Food Anal. Methods (2012) 5:226–233
231
Table 2 TAC and FRAP values of B. purpurea extracts obtained from different extraction techniques Samples
TAC value (mg VCEAC/g extract)
FRAP value (mM Fe2+/g extract)
SBE UBE
219.9±7.04a 377.5±7.53c
2.7±0.04a 4.3±0.04c
MBE
241.6±3.21b
3.1±0.01b
Values were expressed as the mean±standard deviation (n=3). Values followed by different letters in the same column were significantly different (PSBE. HPTLC Densitometric Determination and Bioautography The composition of mobile phase, the amount of sample to be applied and the scan speed were optimised to obtain
Fig. 3 HPTLC densitogram of extracts obtained by different extraction techniques at 366 nm
precise, compact and reproducible bands. HPTLC fingerprint obtained from HPTLC image
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