Table 3.

The proportion of drugs with different rings in the whole database and five sub-databases.

Classes	Number of Rings a	0	1	2	3	>3
All drugs	0	5.8	12.1	16.5	6.6	2.3
	1	3.9	11.1	11.8	3.6	1.1
	2	2.4	4.2	4.2	1.3	0.4
	3	0.9	1.4	1.2	0.3	0.1
	>3	5.2	0.9	0.3	0.3	0
Oral drugs	0	4.5	11.1	15.9	7.5	2.4
	1	3.6	11.6	12.4	4.1	1.0
	2	2.1	4.5	5.1	1.9	0.4
	3	1.0	2.1	1.1	0.1	0.1
	>3	4.4	0.5	0.2	0.2	0
CNS drugs	0	5.3	8.8	18.3	3.8	0.8
	1	5.2	12.0	17.4	4.2	0.7
	2	1.4	4.9	9.7	1.5	0.2
	3	0.1	0.6	1.7	0.2	0
	>3	0.3	0.2	0.1	0.1	0.1
Cardiovascular drugs	0	3.6	14.1	17.3	7.1	3.4
	1	2.0	12.8	12.3	3.1	2.3
	2	2.4	5.3	4.2	1.5	0.2
	3	0.5	0.9	1.2	0.9	0
	>3	2.6	0.5	0.2	0	0
Anti-infective drugs	0	3.3	10.5	17.3	7.8	2.1
	1	4.4	13.0	11.9	2.7	0.3
	2	6.3	4.4	3.8	0.9	0.1
	3	3.3	2.2	0.7	0.1	0.3
	>3	1.9	0.9	0.2	0	0
Anti-cancer drugs	0	11.1	9.5	7.7	7.9	5.0
	1	6.6	6.6	6.8	5.0	1.6
	2	3.2	2.3	2.5	2.9	3.0
	3	0.7	1.4	4.1	0.7	0.2
	>3	2.9	1.1	2.2	3.0	0.4

^a “1, 2, 3, > 3” in row represent the number of aromatic rings. “1, 2, 3, > 3” in column represent the number of non-aromatic rings.