Synergistic effects of acyclovir and 3, 19- isopropylideneandrographolide on herpes simplex virus wild types and drug-resistant strains

Table 1 Cytotoxic effect, anti-viral activity and selective index of IPAD and ACV at the post-entry step

	CC₅₀^a(μM)	Anti-viral activity^bagainst
		HSV-2		HSV-1 KOS		HSV-1 ACGr4		HSV-1 dlsptk		HSV-1 dxpIII
		IC₅₀(μM)	SI^c	IC₅₀(μM)	SI^c	IC₅₀(μM)	SI^c	IC₅₀(μM)	SI^c	IC₅₀(μM)	SI^c
IPAD	39.71	18.01	2.20	16.96	2.34	17.89	2.22	16.86	2.36	17.12	2.32
ACV	>6,400	0.80	>8,000	0.49	>13,061	575.91	>11.11	450.25	>14.21	161.45	>39.64

The value represents mean of three independent experiments.
^aCytotoxic effect was determined using the MTT assay. CC₅₀ was the concentration reducing cell viability by 50% relative to controls.
^bAnti-viral activity was determined using the CPE reduction assay. IC₅₀ was the concentration that reduced HSV-induced CPE formation by 50% relative to controls.
^cSI (selective index) was calculated as the ratio of CC₅₀ to IC₅₀.

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