Phytochemical investigation and antioxidant, antibacterial and anti-tyrosinase performances of six medicinal halophytes

In this study, six medicinal halophytes (Daucus carota, Frankenia laevis, Inula crithmoides, Plantago coronopus, Raphanus raphanistrum and Tamarix gallica) were examined for their phenolic pools, antioxidant (DPPH, ABTS, superoxide radical scavenging and iron-reducing tests), antibacterial (micro-dilution method) and anti-tyrosinase activities. RP-HPLC analysis of the six halophytes showed that D. carota and F. laevis exhibited the highest phenolic contents, with chlorogenic acid (6.6 mg/g DW) and catechin (15.4 mg/g DW) as the major compounds, respectively. In addition, D. carota and F. laevis shoots exhibited the best antioxidant capacities as shown by low IC50 values against DPPH, ABTS, and superoxide anion radicals, and strong iron-reducing capacity. Moreover, F. laevis extracts exhibited a broad-spectrum antibacterial activity against the four human pathogenic strains tested, mainly Micrococcus luteus and Salmonella enterica. D. carota efficiently inhibited Staphylococcus aureus and S. enterica growth. Interestingly, the strongest inhibition of melanin synthesis was found in D. carota and F. laevis, both species inhibiting particularly diphenolase activity. These data suggest that D. carota and F. laevis shoots could be used as effective biomolecules and also as new natural skin-whitening agents.