The Antibacterial Activity of Date Syrup Polyphenols against S. aureus and E. coli

 Plant-derived products such as date syrup (DS) have demonstrated antibacterial activityand  can  inhibit  bacteria  through  numerous  different  mechanisms,  which  may  beattributed to bioactive compounds including plant-derived phenolic molecules. DS is richin polyphenols and this study hypothesized that DS polyphenols demonstrate inherentantimicrobial  activity,  which  cause  oxidative  damage.  This  investigation  revealed  thatDS  has  a  high  content  of  total  polyphenols  (605  mg/100  g),  and  is  rich  in  tannins(357 mg/100 g), flavonoids (40.5 mg/100 g), and flavanols (31.7 mg/100 g) that areknown potent antioxidants. Furthermore, DS, and polyphenols extracted from DS, themost  abundant  bioactive  constituent  of  DS  are  bacteriostatic  to  both  Gram  positiveand  Gram  negativeEscherichia  coliandStaphylococcus  aureus,  respectively.  It  hasfurther been shown that the extracted polyphenols independently suppress the growthof bacteria at minimum inhibitory concentration (MIC) of 30 and 20 mg/mL forE. coliandS. aureus,and have observed that DS behaves as a prooxidant by generating hydrogenperoxide that mediates bacterial growth inhibition as a result of oxidative stress. At sub-lethal MIC concentrations DS demonstrated antioxidative activity by reducing hydrogenperoxide, and at lethal concentrations DS demonstrated prooxidant activity that inhibitedthe growth ofE. coliandS. aureus. The high sugar content naturally present in DS didnot significantly contribute to this effect. These findings highlight that DS’s antimicrobialactivity is mediated through hydrogen peroxide generation in inducing oxidative stressin bacteria.