Table 2.

Anti-HCV activity of andrographolide combination studies with IFN-α and other viral enzyme inhibitors

		CI values at
Combination compound	EC50	EC75	EC90	Influence
IFN-α	0.78 ± 0.015	0.75 ± 0.024	0.73 ± 0.052	Synergistic
Telaprevir	0.72 ± 0.07	0.79 ± 0.035	0.81 ± 0.02	Synergistic
PSI-7977	0.65 ± 0.05	0.69 ± 0.043	0.75 ± 0.022	Synergistic

Ava5 cells were treated with various concentration ratios of andrographolide and each inhibitor targeting NS3/4A protease (telaprevir) or NS5B polymerase (PSI-7977) for 3 days. The tested concentrations are described in Methods section. qRT-PCR was used to determine anti-HCV activity. Combination index (CI) values at effective concentration achieving 50% (EC₅₀), 75% (EC₇₅) and 90% (EC₉₀) inhibition were calculated using CalcuSyn software. As defined by the CalcuSyn program, CI < 1, CI = 1 and CI > 1 indicate synergism, additive effect and antagonism respectively.