Abstract
A food grade compatible enzyme assisted extraction (EAE) technique for extracting bioactive compounds from freeze-dried Kakadu plum puree was evaluated. To optimise the extraction, a central composite rotatable design (CCRD) was conducted and effects of solvent concentration, enzyme concentration and time of reaction on extracted levels of free ellagic acid (fEA), ascorbic acid (AA) and total phenolic content (TPC) were determined. In the extracts, concentration of fEA ranged from 53.6 to 266.6 mg/100 g dry weight (DW) of Kakadu plum puree; AA 63.7 to 112.1 mg/100 g DW and TPC levels of 73.23 to 104.74 mg of gallic acid equivalent (GAE)/g. Extraction yield of fEA ranged from 10.3 to 51.3%. The model was found to be suitable for extraction of fEA - an important bioactive compound with documented antimicrobial properties from Kakadu plum fruit. A solvent (propylene glycol) concentration of 1.5% (w/w), enzyme (pectolytic enzymes) concentration of 300 mg/L and extraction time of 15 h was ascertained as optimum for the fEA extraction delivering a yield of 51.3%. The extraction method described here facilitates the provision of a simple, cost effective food-grade compatible extract that by-passes the need for organic solvents thereby obtaining an EA-rich aqueous extract with enhanced biological activities. This simple extraction method can also be applied to other EA rich plant material like pomegranate and peel of many common fruits which are generated as food processing by-products and can be easily adopted by numerous industries. Key words: Central composite rotatable design, ellagic acid, enzyme assisted extraction, Kakadu plum fruit, Terminalia ferdinandiana.
Highlights
IntroductionKakadu plum is a rich source of polyphenolic compounds for example ellagic acid (EA) and its hydrolysable tannin, ellagitannin (Konczak et al, 2014; Williams et al, 2014)
The present work for the first time, reports the results from non-targeted metabolomic profiling of Kakadu plum fruit. 158 chemically diverse metabolites were identified in the polar extracts including amino acids and their derivatives, fatty acids, organic acids, phenolic acids, steroids, sterols, sugars and sugar alcohol, terpenoids and tocopherol
For the purposes of this study we only report five of the identified sugars namely mannose, rhamnose, galacturonic acid, arabinose glucose and fructose
Summary
Kakadu plum is a rich source of polyphenolic compounds for example ellagic acid (EA) and its hydrolysable tannin, ellagitannin (Konczak et al, 2014; Williams et al, 2014). Konczak et al (2014) reported free EA (fEA) levels of the Kakadu plum fruit are in the range of 3050 to 14020 mg/100 g DW of while a recent study by Williams et al (2014) reported the lower level of 626 to 980 mg/100 g DW of Kakadu plum fruit. The polyphenol EA has been reported to exert anticarcinogenic, anti-bacterial, anti-fungal, antiviral, and antiinflammatory activities (Ahad et al, 2014; Hseu et al, 2012; Sarabhai et al, 2013)
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