Table 1 The components of NCs involved in the review

Herbal extracts

Astragaloside

Calycosin-7-O-β-Glucoside

Extracted from Astragalus, also known as Huangqi in China. It is the dried root of Astragalus mongholicus Bunge. It is widely used as an immune stimulant, an antioxidant, a hepatoprotectant, a diuretic, an antidiabetic, an anticancer drug, and an expectorant. There are more than 100 compounds that have been isolated and identified from this herbal plant.

Salvianolic acids (B&C)

Extracted from the roots of Salvia miltiorrhiza Bunge, also known as Danshen, which is a traditional Chinese medicine for treatment of inflammatory diseases. Salvianolic acid is a polyphenol compound isolated from Danshen and has anti-inflammatory and antioxidant bioactivities.

Ginsenoside

Protopanaxadiol type: Rb1

Protopanaxatriol type: Rg1

Extracted from Panax ginseng (PG), which usually refers to the dried root and rhizome of PG CA Meyer of the family Araliaceae. Recently, clinical studies have shown that compounds or medicines containing different forms of PG have a promising effect on side effects caused by chemotherapy. Ginsenosides, which are the main active ingredient of PG, have a pivotal role in the pharmacological actions of PG.

Wedelolactone

Eextracted from Ecliptae herba with the verified therapeutic effects in some bone diseases such as osteoporosis.

Osthole

7-methoxy-8-(3-methyl-2-butenyl) coumarin, which is a bioactive derivative from coumarin.Extracted from Fructus Cnidii, Radix Angelicae Pubescentis, and other traditional Chinese medicines with a wide range of pharmacotherapeutic effects, including the effects of anti-inflammation and positive effects on osteogenic and neuronal differentiation.

Woody plant-derived bioactive compounds

Berberine

A type of quaternary ammonium alkaloid, extracted from varieties of plants species, such as Coptis and Phellodendron. Berberine hydrochloride is typically used in a clinical setting, due to its numerous pharmacological activities, including anti-microbial, glucose/cholesterol regulatory, survival protection, and immune modulatory properties. Berberine also related to bone remodeling, for instance, inhibited adipogenesis and promoted osteogenesis.

Green tea polyphenols:

Catechins

(EC, EGC, EGCG)

Gallic acid

Caffeine

Extracted from green tea, a common drink brewed from the dried leaves of Camellia sinensis. The main components are phenolic acids, polyphenols (include catechins and gallic acid), caffeine, minerals, and trace amounts of vitamins, amino acids, and carbohydrates. Catechins accounts for more than 80% of green tea polyphenols and are derived from flavan-3- ol. (−)-epicatechin (EC), (−)-epicatechin gallate (EGC), (−)-epigallocatechin (EGC), and (−)-epigallocatechin gallate (EGCG) are the main types of catechins, possessing the most potent antioxidant and free radical scavenging abilities. Gallic acid is also a natural antioxidant which scavenges the superoxide and hydroxyl radicals and prevents oxidative stress. Caffeine, a key xanthine alkaloid element in green tea, is a type of central nervous system stimulant. The excessive caffeine is a risk factor for osteoporosis and bone fracture.

Phytoestrogens

Resveratrol

A nonflavonoid polyphenol phytoalexin with a stilbene structure, and can be found in multiple plants, including the root of white hellebore (Veratum grandiflorum), polygonum cupsidatum, peanuts, eucalyptus, blueberries, cranberries, and grapes. RSV is an effective antioxidant and closely related to SIRT1 pathway, participating in the modulation of apoptosis, DNA repair, oxidative stress resistance, anti-aging processes, and lipid metabolism.

Naringin

A flavonoid compound commonly extracted from citrus fruits and a traditional Chinese medicine Rhizoma Drynariae, which is usually used to treat osteoporosis and bone fracture.