Table 6.

Natural products used for preclinical research.

Name	Intervention approach	Drug dosage	Duration (weeks)	Summary of main findings (compared with IDD group)	References
Resveratrol	Intragastric administration	50 mg/kg/d	4	Decrease Pfirrmann MRI grade; Alcian blue: increase the content of ECM; SA-β-Gal staining: the number of positive cells decreases	[18]
Curcumin	Injected intraperitoneally	100 mg/kg/d	4	Decrease Pfirrmann MRI grade; HE: IVD morphology improvement; immunohistochemistry: collagen II and aggrecan content increased	[68]
Honokiol	Injected intraperitoneally	30 mg/kg/d	4	Decrease Pfirrmann MRI grade; HE and Alcian blue: IVD morphology improved; immunohistochemistry: MMP13 and ADAMATS-5 expression decreased	[74]
	Intragastric administration	40 mg/kg/d	4	Decrease Pfirrmann MRI grade; HE: IVD morphology improvement; immunofluorescence: upregulation of SIRT3 expression	[76]
Salvianolic acid B	Intragastric administration	20 mg/kg/d	6	Decrease Pfirrmann MRI grade; HE, safranin-O fast green, and Alcian blue: IVD shape improvement	[79]
Tea polyphenol	Local injection	100 μM/week	4	Decrease Pfirrmann MRI grade; HE, safranin-O fast green, and Alcian blue: IVD shape improvement; immunohistochemistry: collagen II and aggrecan content increased	[82]
Icariin	Injected intraperitoneally	30 mg/kg/d	8	Decrease the Pfirrmann MRI grade; increase the height of the IVD; immunohistochemistry: aggrecan content increased; TUNEL: decreased rate of positive cells	[93]
Naringin	Injected intraperitoneally	80 mg/kg/d	4 and 12	Decrease Pfirrmann MRI grade; HE: IVD morphology improved	[101]
Genistein	Intragastric administration	100 mg/kg/d	4	X-ray: increased intervertebral space height; HE: improved IVD morphology; Immunofluorescence: upregulated expression of Nrf2	[107]
	Local injection	5 μg/mL, 10 μg/mL, 20 μg/mL/week	2 and 4	Decrease Pfirrmann MRI grade; HE: improve the structure of the intervertebral disc in a dose-dependent manner; immunohistochemistry: increase the expression of collagen II in a dose-dependent manner	[108]
Wogonin	Local injection	50 μM/week	4 and 8	Decrease Pfirrmann MRI grade; HE: IVD morphology improvement	[111]
Luteoloside	Injected intraperitoneally	10 mg/kg/d	4 and 8	Decrease the Pfirrmann MRI grade; X-ray: increased intervertebral space height; HE and safranin-O fast green: IVD morphology improvement	[114]
Quercetin	Injected intraperitoneally	100 mg/kg/d	8	X-ray: increased intervertebral space height; HE and safranin-O fast green: IVD morphology improvement; immunofluorescence: downregulation of caspase-3 expression, upregulation of SIRT1 expression	[117]
Berberine	Injected intraperitoneally	150 mg/kg/d	8	Decrease Pfirrmann MRI grade; HE and safranin-O fast green: IVD morphology improvement; TUNEL: decreased rate of positive cells	[128]
	Intragastric administration	150 mg/kg/d	4	Decrease Pfirrmann MRI grade; HE: IVD morphology improvement; immunofluorescence: downregulation of caspase-3 expression	[129]
Oxymatrine	Local injection	Oxymatrine 10 μM; Oxymatrine 10 μM + LIP100 μg/μL	4	X-ray radiology: oxymatrine-LIP can partially restore the height of the IVD	[132]