Optimization of Cat’s Whiskers Tea (Orthosiphon stamineus) Using Supercritical Carbon Dioxide and Selective Chemotherapeutic Potential against Prostate Cancer Cells

Table 3

Antioxidant activities of the extracts of O. stamineus leaves obtained by supercritical CO₂.

Assays^a	IC50 values^d of the samples in μg/mL
	A1	A2	A3	B1	B2	B3	C1	C2	C3	AA
ABTS^b	ND	1150	ND	ND	91.7*	ND	218	ND	117	6.5**
DPPH^c	>200	>200	>200	136	42.8*	164	168	56.1**	198	5.8**

Microtiter 96-well plate was used to assess the concentrations (12.5, 25, 50, 100, and 200 μg/mL) of test samples. Methanol was used as blank. ABTS or DPPH was used as negative control. Ascorbic acid (AA) was used as reference standard.
^bAbsorbance for ABTS was measured at 734 nm.
^cAbsorbance for DPPH was measured at 517 nm.
^dUsing linear regression curves the median inhibitory concentrations (IC₅₀) were calculated. The results are expressed as mean ± SD ( = 6); * < 0.05; ** < 0.01.