Table 4.

The proportion of drugs containing only aromatic rings, only non-aromatic rings, both aromatic and non-aromatic rings, no rings and bridge rings in the whole database and five sub-databases.

Classes a	Only Aromatic Rings	Only Non-Aromatic Rings	Both Aromatic and Non-Aromatic Rings	No Rings	Bridge Rings
All drugs	37.5 (12.1, 16.5) b	12.4	42.0 (11.1, 11.8) c	5.8	2.4
Oral drug	36.9 (11.1, 15.9) b	11.1	45.2 (11.6, 12.4) c	4.1	2.3
CNS drugs	31.7 (8.8, 18.3) b	7.0	53.6 (12.0, 17.4) c	5.3	2.4
Cardiovascular drugs	42.0 (14.1, 17.3) b	7.3	45.3 (12.8, 12.3) c	3.6	1.7
Anti-infective drugs	37.8 (10.5, 17.3) b	15.9	41.5 (13.0, 11.9) c	3.3	1.4
Anti-cancer drugs	30.1 (9.5, 7.7, 7.9) d	13.3	43.7 (6.6, 6.8, 5.0) e	11.1	1.8

^a The captions in each row represent drugs containing different rings; ^b The numbers in brackets represents the proportions of drugs with one aromatic ring and two aromatic rings, sequentially; ^c The numbers in brackets represents the proportions of drugs with one aromatic ring and one non-aromatic ring, two aromatic rings and one non-aromatic ring, sequentially; ^d The numbers in brackets represents the proportions of drugs with one aromatic ring, two aromatic rings and three aromatic rings, sequentially; ^e The numbers in brackets represents the proportions of drugs with two aromatic rings and one non-aromatic ring, two aromatic rings and two non-aromatic rings, two aromatic rings and three non-aromatic rings, sequentially.