Antimicrobial and antioxidant activities of the leaf extract of some cultivated Iranian licorice populations

Licorice (Glycyrrhiza glabra L.) is a well-known commercial medicinal plant with wide usage.

During our ongoing aims for the selection and breeding programs of Iranian licorice (Glycyrrhiza glabra L.) populations, in the present study, total phenol content (TPC), total flavonoid content (TFC), and biological activities of the leaf extract of eight selected plant populations cultivated in the north of Tehran were investigated.

The TPC and TFC were determined by Folin-Ciocalteu and aluminum chloride reagents, respectively. The antioxidant potential of the leaf extracts was measured through the evaluation of their power to reduce the Fe3+-TPTZ complex to Fe2+-TPTZ. The antibacterial activity was also assessed according to the broth micro-dilution method to determine minimum inhibitory concentration.

The results indicated that TPC varied from 6.18 ± 0.33 (mg GAE/g DW) in Bajgah population to 14.91 ± 1.17 (mg GAE/g DW) in Ilam population. The highest TFC was observed in Ilam (17.04 ± 1.25 mg rutin/g DW) and Marvest (15.06 ± 1.77 mg rutin/g DW) populations, respectively, without statistically significant differences. The maximum antioxidant activity was associated with the Ilam (532.18 ± 12.61 µmol Fe/g DW) population, confirming the antioxidant potential of phenolic and flavonoids compounds. The leaf extracts of Eghlid, Marvest, Ilam, and Bojnourd populations were exhibited outstanding antibacterial activity against S. aureus.

The licorice leaf extracts showed more inhibitory effect against Staphylococcus aureus than Escherichia coli.