Determination of Antioxidant, Antimicrobial and Metal Chelating Properties of Bioactive Compounds in Sepioteuthis Lessoniana Ink
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Date
2014
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Uva Wellassa University of Sri Lanka
Abstract
Big fin reef squid (Sepioteuthis lessoniana) is a widely distributed species in Northern coast of Sri Lanka and generates 52% of total body weight as waste due to high utilization in processing industry while causing a series of ecological problems and environmental pollution. As these by-products are a potential source of good bioactive compounds, this study aimed to analyze the bioactive properties of hydrolysates developed from squid crude ink. Ink sacs of S. lessoniana were collected and squeezed. Moisture, protein, ash and lipid content in crude ink were analyzed. Trypsin (1:100) was used in the preparation of enzymatic hydrolysates from lyophilized ink at pH of 7.8 by incubating at 37°C for 0, 3, 6, 9, 12 and 24 hours followed by heat inactivation at 100°C
for 15 minutes. Best time course (3 hours) was detected using 15% SDS-PAGE and
directed to develop chemical hydrolysates using 6 M NaOH (basic), 6 M HC1 and 6 M
Acetic acid (acidic) in 2:1 ratio respectively while incubating at 37°C for 3 hours
followed by heat inactivation at 100°C for 15 minutes and 15% SDS-PAGE was
conducted. DPPH radical scavenging assay was used to detect antioxidant activity, metal chelating activity was used to detect Fe2+ chelating activity while agar well diffusion method was used to detect antimicrobial activity in selected best hycfrolysates. According to the proximate analysis, moisture and protein contents were 75.53±2.10% and 19.73±2.44% respectively in crude ink. DPPH scavenging assay showed a significant difference between the treatments (p<0.05) and Fe2+ chelating activity assay revealed that there was no significant difference among those three hydrolysates (p>0.05). However, highest DPPH scavenging activity and Fe2+ chelating activity values (61.54±2.96% and 30.35±3.91%) were obtained from acid hydrolysis. The results obtained from antimicrobial assay revealed that the highest inhibition zones were from hydrolysates developed from acids. Accordingly, the study concluded that hydrolysates produced by incubating with 6 M HC1 and 6 M Acetic acid for 3 hours followed with heat inactivation has better antioxidant, antimicrobial and metal chelating activities compared to rest.
Keywords: Squid ink, Enzymatic hydrolysates, Chemical hydrolysates, Antioxidant,
Metal chelating
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Aquatic Resources Technology Degree Programme ( AQT)