Table 2.

Structure-activity relationships for the main categories of derivatives.

The position of the modification	Representative derivatives	Activities	References
A ring		Antibacterial activity	[105]
		Antiparasitic activity	[106]
		Inhibitors against hCE1	[107]
C-28		Inhibitory effect on serotonin	[108]
		Promoting osteoblast activity
C ring		Hepatoprotective effect	[109]
A ring and c-28 (amidation)		Antitumor activity	[109]
		Protective effect of cardiomyocytes
			[110]
A ring and c-28 (esterification)		Antimicrobial activity	[111]
		Antitumor activity	[112]
A ring and c-28 (nitrogen-containing heterocycle)		Antitumor activity	[113]