Physicochemical properties and phenolic composition of selected Saskatchewan fruits : buffaloberry, chokecherry and sea buckthorn

There is increasing interest in the commericalization of native fruits for utilization as foods and medicinal extracts. This study was undertaken to determine the physicochemical properties and phenolic composition of selected Saskatchewan native fruits, including buffaloberry (Shepherdia argentea Nutt.), chokecherry (Prunus virginiana L.) and sea buckthorn (Hippophae rhamnoides L.). The physicochemical analyses included carbohydrate content, CIELAB colour values, organic acid composition, phenolic content, % seed, soluble solids, pH, total solids, total titratable acidity and proximate composition. Fruit samples were collected and analyzed over four crop years. The proanthocyanidin content was also determined photometrically after acid depolymerization in acid-butanol. Buffaloberry contained a proanthocyanidin concentration of 505 ± 32 mg/100 g fresh fruit and this level was 10 fold higher than that of chokecherry and sea buckthorn. Chokecherry was found to contain an anthocyanin concentration of 255 ± 35 mg/100 g fresh fruit, as determined using the pH differential method. Two high performance liquid chromatography (HPLC) methods were developed for simultaneous determination of seven phenolic classes, including anthocyanins, hydroxybenzoic acids, hydroxycinnamic acids, flavanols, flavanones, flavones and flavonols in aqueous methanol extracts. Based on the semi-quantitative analysis of the total phenolic chromatographic index (TPCI), chokecherry contained the highest levels of phenolic compounds with a concentration of 3,327 ± 469 µg/g fresh fruit followed by buffaloberry (578 ± 73 µg/g fresh fruit) and sea buckthorn (477 ± µg/g fresh fruit). The antioxdant activity of the fruit extracts was determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2´-azinobis-3-ethylbenzthiazoline-sulphonic acid (ABTS) radical scavenging assays. Buffaloberry and chokecherry produced the highest radical scavenging activity and were at least five fold greater than that of sea buckthorn. The major radical scavenging compounds in buffaloberry were ascorbic acid and proanthocyanidins. Radical scavenging activity of chokecherry fruit was largely attributable to its anthocyanins, flavonols and hydroxycinnamic acids. Prominent antioxidants in sea buckthorn included ascorbic acid, proanthocyanidins and flavonols. Certain individual compounds in the phenolic extracts were identified by HPLC-photodiode array and HPLC-mass spectrometry. Rutin was found in all of the extracts. Other phenolic compounds identified included catechin in sea buckthorn, and chlorogenic acid and quercetin in chokecherry. The chokecherry fruit pigments were comprised of two major anthocyanins and these were identified as cyanidin 3-glucoside and cyanidin 3-rutinoside. A preparative scale purification method for these anthocyanins using centrifugal partition chromatography (CPC) was determined. Under the CPC conditions employed, cyanidin 3-glucoside and cyanidin 3-rutinoside were purified to concentrations of 84 and 90%, respectively