Table 3. The cytotoxic effect of TPP⁺-benzoates on HNSCC cell lines (Cal27, HEp-2, SCC-15) and oral keratinocyte (OKF-6/TERT), and selectivity index IC₅₀ = the concentration required to induce cytotoxicity effects in 50% of HNSCC cells and oral keratinocyte cells after 48 h of treatment. Compounds BA-C₁₀ (benzoic acid decyl ester), and PIA-C₁₀ (2,3-dihydroxybenzoic acid decyl ester) were used as controls to evaluate the effects of inclusion of TPP⁺ moiety in compounds (structures in Fig. 1). Each assay was performed in triplicate. Key: *p ≤ 0.05 with respect to the effect of TPP⁺C₁₀ (3,4,5-trihydroxybenzoic acid decyl ester) at the same cell line time; ***p ≤ 0.001 with respect to the effect of TPP⁺C₁₀ at the same cell line and time; a = p ≤ 0.05 respect to the effect at the same time in Cal-27 cell line.

Compounds	IC50 at 48 h (μM)
	Cell lines
	Cal-27	HEp-2	SCC-15	OKF-6/TERT
SA-TPP + C 10 (5be)	2.3 ± 0.06*	4.28 ± 0.12	3.2 ± 0.2	12.7 ± 0.2a
GA-TPP + C 10 (5bd)	2.2 ± 0.02*	5.66 ± 1.09	2.7 ± 0.1*	13.2 ± 0.4a
PIA-TPP + C 10 (5bb)	1.6 ± 0.01*	8.28 ± 0.27	2.9 ± 0.07	7.5 ± 0.1a
TPP + C 10 (5ba)	3.4 ± 0.1	12.52 ± 0.94	3.0 ± 0.09	13.1 ± 0.4
Cisplatin (CDDP)	4.7 ± 0.9	5.2 ± 0.7	12.5 ± 1.2	3.2 ± 0.2