Phellodendri Cortex: A Phytochemical, Pharmacological, and Pharmacokinetic Review

Phellodendri Cortex (PC) or Huang Bai. According to the scientific database of China Plant Species and Chinese pharmacopeia 2015 edition, PC has two main species which are Phellodendron amurense Rupr (PAR) or "Guan Huang bai" in Chinese and Phellodendron chinense Schneid (PCS) or "Chuan Huang bai" in Chinese. The crude drugs of PAR and PCS are also called Phellodendri amurensis cortex (PAC) and Phellodendri chinense cortex (PCC), respectively. The medicinal part of the plant is the dried trunk bark. PC has comprehensive therapeutic effects which include anti-inflammatory, antimicrobial, anticancer, hypotensive, antiarrhythmic, antioxidant, and antipyretic agents. The exact ingredients in PC and its species are not fully summarised.

This study was designed to review and evaluate the pharmacological actions of compounds and to explore the pharmacokinetic knowledge of PC and its species and to also identify the chemical compound(s) with a potential therapeutic effect on atopic dermatitis.

"Huang Bai" and its English, botanical, and pharmaceutical names were used as keywords to perform database search in Encyclopaedia of traditional Chinese Medicines, PubMed, EMBASE, MEDLINE, Science Direct, Scopus, Web of Science, and China Network Knowledge Infrastructure. The data selection criteria included all the studies that were related to the phytochemical, pharmacological, and pharmacokinetic perspectives of PC and its species or their active constituents. More importantly, the voucher number has been provided to ensure the genuine bark of PC used as the medicinal part in the studies.

140 compounds were summarized from PC and its species: specifically, 18 compounds from PCC, 44 compounds from PCS, 34 compounds from PAC, and 84 compounds from PAR. Obacunone and obaculactone are probably responsible for antiatopic dermatitis effect. PC and its species possess a broad spectrum of pharmacological actions including anti-inflammatory effect, antibacterial effect, antiviral effect, antitumor effect, antigout effect, antiulcer effect, neuroprotective effect, and antiatopic dermatitis effect. PC could widely distribute in plasma, liver, spleen, kidney, and brain. Berberine may be responsible for the toxic effect on the susceptible users with hemolytic disease or in the peripartum and neonatal period.

The compounds of the crude bark of PC and its subspecies have showcased a wide range of pharmacological effects. Pharmacological efficacies of PC are supported by its diverse class of alkaloid, limonoid, phenolic acid, quinic acid, lignan, and flavonoid. Obacunone and obaculactone could be the bioactive compounds for atopic dermatitis management. PC and its subspecies are generally safe to use but extra care is required for certain conditions and group of people.