TOTAL PHENOLICS AND ANTIOXIDANT PROPERTIES OF DATE PALM (PHOENIX DACTYLIFERA L.) PITS AS AFFECTED BY CULTIVAR AND LOCATION

Pits of date palm (Phoenix dactylifera L.) fruit constitute about 10 to 15% of the fruit weight and contain fats, carbohydrates, minerals, proteins, steroids, vitamins, phenols, and crude fibers. Although of potentially useful nutritive content, pits generally have had no specific use and are commonly discarded, other than sometimes they may be used as organic fertilizers, as feed supplement for livestock and activated charcoal. There is also an increasing interest in using date pits to produce a caffeine-free hot beverage similar to coffee. Pits of 15 cultivars were collected from the USA and Saudi Arabia in 2006 and 2007 to characterize and compare total phenolics (TP) content and antioxidant capacity and to study the difference between ABTS [-2,2’ Azino-bis (3-ethylbenzo-thiazoline-6-sulfonic acid) diammonium Salt ~98%] and DPPH (2,2-Diphenyl-1-picrylhydrazyl) methods in measuring antioxidant capacity. Pits of the cultivars collected from Saudi Arabia had higher dry matter content than those collected from the USA. In most of the tested cultivars, total phenolics content was significantly higher during the first year of the study. Pits of ‘US6’ cultivar (‘Hilali’) had the highest total phenolics content (66.7 mg GAE/100 g DW) during the first year of the study followed by ‘SA3’ cultivar (‘Deglet Noor’) which had a total phenolics content of 66.4 mg GAE/100 g DW. The lowest content was found in the pits of ‘US1’ cultivar (‘Amir Hajj’) (14.5 mg GAE/100 g DW) followed by ‘US5’ cultivar (‘Hayany’) (16.4 mg GAE/100 g DW) and ‘US2’ cultivar (‘Barhee’) (24.6 mg GAE/100 g DW respectively). The pits of ‘US3’ (‘Deglet Noor’), ‘US6’ (‘Hilali’), ‘US10’ (‘Zahidi’) and ‘SA3’ (‘Sukari’) cultivars had higher antioxidant capacity as measured by both ABTS and DPPH during the first year as compared to the second year of the study while the pits of ‘US7’ (‘Khadrawy’) and ‘SA1’ (‘Amir Hajj’) cultivars had higher antioxidant capacity during the second year of the study. Mean separation tests indicated that first year samples had higher antioxidant capacity than those of the second year as measured by either ABTS or DPPH. ABTS ranged from 53.1 to 679.0 µmole TEAC/100 g of dry weight in ‘US5’ (‘Hayany’) and ‘US6’ (‘Hilali’) respectively. Although ABTS analysis had a higher antioxidant capacity as related to the total phenolics contents in most cultivars, DPPH analysis had higher reproducibility. Over all cultivars tested from both years, the antioxidant capacity as related to total phenolics content was higher in samples collected from Saudi Arabia. The pits of different date palm cultivars have different physical and chemical characteristics including dry matter content, total phenolics content and antioxidant capacity. The total phenolics assay may be a good indicator of antioxidant properties in date pits.