TABLE 1.

Some natural bioactive compounds shown to modulate ACE2 prior to the COVID-19 era.

Natural products	Bioactive compound	Method of assessment	References
Flavonoids	Naringenin apigenin	In vivo	(Sui et al., 2010; Wang et al., 2019)
	Baicalin	In vivo	(Wei et al., 2015)
Steroids and steroids glycosides	Ginsenoside Rg3	In vivo	(Liu et al., 2019)
Coumarins	Osthole	In vivo	(Shi et al., 2013; Hao and Liu, 2016)
Alkaloids	Nicotianamine	In vitro	(Takahashi et al., 2015)
	Emodin	In vitro	(Ho et al., 2007)