Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Comparison of Total Antioxidant Capacities and Principle Components With Antioxidant Capabilities of Some Apple Varieties Produced in Turkey

Phenolic compounds abundant in plants that prevent many risk-posing diseases for human health (essentially cancer, coronary & cardiovascular diseases, diabetes, etc.) are named as biologically active compounds and addressed in many studies. One of the most important features of these compounds is their antioxidant activity for scavenging free radicals that emerge as a result of metabolic reactions. These compounds present in fruits, vegetables and many other vegetal products are responsible for colour, flavour, and taste of plants, as well as affecting food quality.

Since apple is a relatively cheap fruit having a unique taste for all choices and a long durability in all seasons of the year, it is one of the most consumed fruits. Consequently, it was aimed in this study to qualitatively and quantitatively compare the total antioxidant capacities and the components affecting this capacity of various apple varieties produced in our country such as King Luscious, Amasya, Sky Spur, Ervin Spur, Arap Kizi, Lutz Golden, and Granny Smith.

Experimental studies were performed by determining the total antioxidant capacities of apple parts arising from antioxidant compounds using two spectrophotometric methods, firstly the simple and low-cost CUPRAC (Cupric Ion Reducing Antioxidant Capacity) method developed in our laboratory, and secondly the ABTS (2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonate) reference method accepted in international literature for antioxidant assays, and by identification and quantitation of the leading antioxidant constituents individually with HPLC. The CUPRAC method was applied for the first time to phloridzin, procyanidine and cyanidine chloride. Spectrophotometric and chromatographic analysis data were compared.

The concentrations of antioxidant constituents in apple parts assayed with HPLC were as follows: apple juices: ascorbic acid (22 - 88 mg L-1), catechin (9.09 - 115.30 mg L-1), chlorogenic acid (41.10 - 276.3 mg L-1), epicatechin (3.38 - 66.76 mg L-1), caffeic acid (3.04 - 79.09 mg L-1) and phloridzin (0.52 - 20.13 mg L-1); apple peel extracts: ascorbic acid (0.10 - 0.37 mg g-1), phloridzin (0.08 - 0.52 mg g-1), catechin, chlorogenic acid and epicatechin (trace amounts), and quercetin glycosides {converted to quercetin (1.02 - 2.94 mg g-1)}; pulp extracts: ascorbic acid (2.0 x 10-2 - 5.0 x 10-2 mg g-1), catechin (0.71 x 10-2 - 16.0 x 10-2 mg g-1), chlorogenic acid (1.7 x 10-2 - 10.4 x 10-2 mg g-1), epicatechin (0.95 x 10-2 - 5.6 x 10-2 mg g-1), caffeic acid (0.39 x 10-2 - 9.06 x 10-2 mg g-1) and phloridzin (0.39 x 10-2 - 1.6 x 10-2 mg g-1). These constituents were found in variable amounts with respect to apple varieties.

Apple pulp has lower antioxidant contents and therefore lower antioxidant capacity than apple peel and juice. The importance of the consumption of apples together with peels for human health was reconfirmed in this study. The order of antioxidant capacities of apples (mmol trolox g-1) determined with the CUPRAC method were: Granny Smith (0.178 ± 0.001) > Amasya (0.156 ± 0.002 ) > Sky Spur (0.139± 0.001) ≥Ervin Spur (0.132 ± 0.002) > King Luscious (0.118 ± 0.002) ≥ Arap Kizi (0.113 ± 0.002)  Lutz Golden (0.111 ± 0.001) It was seen that among apples of native origin, Amasya is superior to Arap Kizi in terms of total antioxidant capacity.