Date (Phoenix dactylifera) seed and syringic acid exhibits antioxidative effect and lifespan extending properties in Caenorhabditis elegans

Date fruit (Phoenix dactylifera (PD); Arecaceae) has numerous proven health benefits and is the staple food in the Middle East. The seed which is discarded forms one-fourth of its weight and is rich in polyphenols. However, the possible effect of PD seed (PDS) extract in Caenorhabditis elegans has not been reported. The objective of this investigation was to provide the first scientific based results of the in vivo antioxidant effect of the PDS extract and its active ingredient in a Caenorhabditis elegans animal model system. The composition of a methanol extract of PDS was analyzed by RP-HPLC. Ferric reducing antioxidant power (FRAP) and hydrogen peroxide scavenging assays were performed for the estimation of in vitro antioxidant activity of the crude extract and one of its components – syringic acid (SA). For the in vivo effect, worms were exposed to different concentrations of PDS extract and SA. Lifespan and oxidative stress response were analyzed. To investigate the pathway involved, transgenic strains (mu86, DAF-16::GFP) of C. elegans were used. The amount of syringic acid in the phenolic content of the extract was 10.72 µg/mL. PDS and SA demonstrated antioxidative property in concentration dependent fashion and a concentration of 250 µg/mL PDS and 600 µg/mL SA significantly increased the lifespan and provided indemnity against pro-oxidants. The effect was independent of the DAF-16 transcriptional regulator as observed by using DAF16::GFP nuclear translocation assays and a daf-16 null mutant strains. The fertility also increased upon treatment with PDS and SA. This implicates syringic acid as a possible drug and date seed powder can thence be further investigated to be used as a dietary nutritional supplement.