Table 2.

HPLC calibration curves of reference compounds including regression equations, the coefficients of determination (R ²), and calibration ranges.

Reference compound	Regression equation	R 2	Calibration range	Mass percentage
Dracorhodin perchlorate	y = 2000000x − 19368	0.999	0.0125–0.2 μg	0.15%
Catechin	y = 26508x − 35003	0.997	0.25–4 μg	24.2%
Epicatechin	y = 33500x − 65614	0.999	0.5–4 μg	1.7%
Acetyl-11-keto-β-boswellic acid	y = 79427x − 54832	0.999	0.125–2 μg	1.62%
(E)-Guggulsterone	y = 2466634x + 12554	0.999	0.0625–1 μg	0.02%