Table 2.

Antibacterial susceptibility (MIC, µg ml⁻¹), efflux ratios, and ribosomal affinity IC₅₀ (µM) against Mycobacterial species

	M. tuberculosis H37Rv			M. abscessus ATCC 19977			M. smegmatisa
Compound	WT MIC (µg ml−1)	∆1258c MIC (µg ml−1)	Efflux Ratio	WT MIC (µg ml−1)	∆2780c MIC (µg ml−1)	Efflux Ratio	WT MIC (µg ml-1)	Ribo. IC50 (µM)
SPC (1)	64	4	16	512	16	32	64	0.80b
TroSPC (2)	32	2	16	64	16	4	32	0.51
SPA (3)	2	4	0.5	64c	16c	4c	ND	1.80d
TroSPA (4)	2	1	2	64	16	4	32	2.45
bAmSPC (5)	16	2	8	128	8	16	ND	1.18b
bAmTroSPC (6)	8	1	8	64	64	1	64	2.49
eAmSPC (7)	2	0.5	4	4	1	4	4	1.01b
eAmTroSPC (8)	2	0.25	8	8	8	1	8	2.31
Amino TroSPC (11)	16	2	8	64	64	1	32	0.64
AmTroSPC (13)	64	8	8	64	64	1	128	2.71

^aMIC assays were conducted using M. smegmatis strain MC² 155. Ribosome inhibition assays were conducted using ribosomes purified from M. smegmatis strain SZ380

^bRibosomal IC₅₀ for compounds 1, 5, and 7 were previously reported in ref. [20]

^cLead SPA 1810 (Compound 39 from ref. [16]) was substituted for SPA 3. SPA 1810 possess an additional hydroxyl on the para position of the pyridine ring when compared to SPA 3

^dRibosomal IC₅₀ used for compound 3 was converted from µg/mL to µM from what was previously reported in ref. [16]