Table 1. Summary of GRIND variables and their corresponding distances identified as highly correlated to biological activity (−logIC₅₀) of compounds.

Probes	Distances (Å)	Features	Impact	Comments
N1–N1	8.00–8.40	OH C=O	+	COOH group at meta position of piperidine, pyrrolidine, or azetidine ring has shown positive contribution towards hGAT1 inhibition activity (IC50)
	14.00–14.40	C=O –O–	−	Carbonyl oxygen of the COOH group and the ether group present either in the linker region or in the bulky aromatic substituents has shown negative contribution towards the biological activity.
O–N1	5.60–6.00		+	Distance between protonated nitrogen of the piperidine, pyrrolidine, or azetidine ring and the COOH group
	10.40–10.80		−	Protonated nitrogen of the piperidine ring and the methoxy substitution of the diaryl moieties
DRY–N1	10.40–10.80	Di/tri aryl moieties COOH	+	Distance between COOH group of piperidine, proline, pyrrolidine, or azetidine ring and bulky aromatic rings after linker chain
	6.40–6.80	Di/tri aryl moieties –O–	−	Distance between aromatic moieties and the ether group in the linker region
O–O	6.00–6.40	–O– X atom (any electronegative atom e.g., F, Cl−, O−, F−)	−	Depicts a distance between the ether group of hydrophilic chain and methoxy or flouro group attached at para position of aromatic rings
TIP–TIP	12.40–12.80	OCH3 OCH3	−	Distance between the methoxy substitutions on aromatic moieties attached at the linker region of hGAT1 antagonists