Phytochemical analysis and evaluation of the cytotoxic, antimicrobial and antioxidant activities of essential oils from three Plectranthus species grown in Saudi Arabia

Table 4 Antioxidant activity and free radical scavenging activity of the essential oils of Plectranthus species

Samples	^aTotal antioxidant Activity in % (1000 μg/mL)	Free Radical Scavenging Activity in % (DPPH-radical scavenging assay)
Samples	^aTotal antioxidant Activity in % (1000 μg/mL)	10	50	100 (μg/mL)	500	1000
P. cylindraceus	71.1 ± 4.5a	25.1 ± 4.2c	39.4 ± 3.5a	50.2 ± 4.3	70.5 ± 3.9a	75.9 ± 4.0b
P. asirensis	52.5 ± 4.9a	15.6 ± 3.9b	20.4 ± 3.8c	36.9 ± 1.6a	46.5 ± 4.1	55.1 ± 2.9b
P. barbatus	62.9 ± 5.1b	21.1 ± 4.8b	30.5 ± 4.1a	44.5 ± 3.1b	60.6 ± 3.8c	68.2 ± 3.2a
Ascorbic acid	NT	81.4 ± 5.2	87.2 ± 3.8	91.0 ± 4.5c	93.0 ± 3.8a	94.1 ± 4.4c
Rutin	88.2 ± 5.1b	NT	NT	NT	NT	NT

^aβ-carotene bleaching assay, NT not tested. In the columns, means ± SD with different letters notification are significant at (P < 0.05) (n = 3)