Synergistic growth inhibitory effects of Phyllanthus emblica and Terminalia bellerica extracts with conventional cytotoxic agents: Doxorubicin and cisplatin against human hepatocellular carcinoma and lung cancer cells

Table 1 IC₅₀ values of individual herbal extracts in human cancer cells and normal cells

Extract	IC50 value (&mgr;g/mL)
	A549b	HepG2b	Vero (Normal)
P. emblica	12.18 ± 5.83	30.47 ± 6.67	157.86 ± 14.90
T. bellerica	27.07 ± 2.19	82.39 ± 27.09	238.70 ± 8.45

Data are shown as mean ± SD from three separate experiments.

^bP < 0.01 represents the statistical significance between normal cell (Vero) and each cancer cell (A549 and HepG2).

Table 2 IC₅₀ values of chemotherapeutic drugs in human cancer cells

Drug	IC50 value (&mgr;g/mL ± SD)
	A549	HepG2
Doxorubicin	0.170 ± 0.006	0.511 ± 0.025
Cisplatin	1.04 ± 0.21	1.05 ± 0.18

Data are shown as mean ± SD from three separate experiments.

Table 3 Dose-effect relationships of extracts and drug combinations in human cancer cell lines

Cell line	Single extracts, drugs and combinations	Parameters			CI value at			DRI value at
		Dm (&mgr;g/mL)	m	r	IC50	IC75	IC90	IC50	IC75	IC90
A549	P. emblica	36.75	0.71	0.99				2.67	3.90	5.67
	Doxorubicin	0.164	0.78	0.99				1.64	2.07	2.60
	(D)1 + (D)2 (4:0.029)	13.75 + 0.100	0.93	0.99	0.98	0.74	0.56
	T. bellerica	17.78	1.57	0.86				1.26	0.85	0.57
	Doxorubicin	0.169	0.87	0.99				1.66	1.95	2.30
	(D)1 + (D)2 (4:0.029)	14.11 + 0.102	1.00	1.00	1.40	1.69	2.18
	P. emblica	18.75	0.75	0.95				1.65	2.63	4.19
	Cisplatin	0.596	0.99	0.96				2.09	2.33	2.59
	(D)1 + (D)2 (40:1)	11.38 + 0.285	1.09	0.98	1.08	0.81	0.62
	T. bellerica	30.36	0.95	0.97				1.76	1.87	1.99
	Cisplatin	1.228	1.36	1.00				2.85	2.15	1.62
	(D)1 + (D)2 (40:1)	17.26 + 0.431	1.00	1.00	0.92	1.00	1.12
HepG2	P. emblica	157.82	2.65	0.98				1.47	1.26	1.07
	Doxorubicin	0.584	1.04	0.96				4.69	7.58	12.23
	(D)1 + (D)2 (25:0.029)	107.23 + 0.124	1.92	0.94	0.89	0.93	1.02
	T. bellerica	150.34	3.11	0.95				1.37	1.07	0.84
	Doxorubicin	0.569	1.04	0.95				4.48	7.09	11.24
	(D)1 + (D)2 (25:0.029)	109.66 + 0.127	1.83	0.97	0.95	1.07	1.28
	P. emblica	111.59	2.18	0.99				1.24	1.08	0.94
	Cisplatin	0.839	0.91	0.95				2.32	4.08	7.19
	(D)1 + (D)2 (250:1)	90.395 + 0.362	1.72	0.96	1.24	1.17	1.20
	T. bellerica	111.02	2.26	1.00				1.19	1.01	0.85
	Cisplatin	0.881	1.13	0.98				2.36	3.26	4.49
	(D)1 + (D)2 (250:1)	93.30 + 0.373	1.68	0.99	1.26	1.30	1.40

Dose-effect relationships were calculated by the median-effect equation. D_m median-effect dose (concentration in &mgr;g/mL that inhibits cell growth by 50%), m shape of the dose-effect curve (where m = 1, m > 1, and m < 1 indicate hyperbolic, sigmoidal, and negative sigmoidal curves, respectively), r linear correlation coefficient of the median effect plot (indicates conformity of data). CI was calculated by Chou and Talalay’s CI equation. CI < 1, CI = 1, and CI > 1 indicate synergism, additive effect, and antagonism, respectively. D_m and m values for single drugs, extracts and their combinations were used in the equations Dx = Dm [f_a/(1) f_a)]^1/m and CI = (D)₁/(Dx)₁ + (D)₂/(Dx)₂. f_a fraction affected by D (e.g. 0.9 if cell growth is inhibited by 90%), (D)₁ and (D)₂ combined doses of extract 1 and drug 2 for x% inhibition, (Dx)₁ and (Dx)₂ doses of the single extract 1 and drug 2 for x% inhibition. DRI dose reduction index was measured by comparing the doses required to reach a given degree of inhibition when using the drug as a single agent and in combination.