Role of borneol as enhancer in drug formulation: A review

As a traditional Chinese medicine (TCM), borneol has shown superior ability for anti-inflammatory and analgesic activities when coupled with other active ingredients from ancient times. Furthermore, borneol is believed to improve blood concentration and bioavailability of drugs. Thus, it has been paired with various TCM formulas since ancient time. The physiological barriers in human can cause significant limitations in drug efficiency as the drug is primarily restricted from entering into blood and brain. Borneol has been proven to enhance the permeability of biological barriers such as the blood–brain, transdermal, corneal, and intestinal barriers. Moreover, growing interest has been shown in the drug delivery system design for trans-barrier transport involving borneol. Nano-drug delivery system with increased surface area and improved active sites, has been applied to increase the bioactivity of water insoluble drugs. Nano-drug delivery system has been used to enhance drug efficacy by reducing the time of action as compared to conventional administration approach of TCM formulas. Given its ability to enhance cross-barrier permeation and drug efficacy, borneol has been integrated into TCM formulas of drug delivery system for precise and prolonged targeting at tumor sites. However, the design and preparation of a drug delivery system consisting of borneol still face great challenges. Current research fails to unravel the difference in mechanism of action between nano-drug delivery systems comprised of borneol and conventional drug systems coupled with borneol. Enhanced penetration of borneol in drug delivery system is rarely verified compared to conventional administration with identical drug formulation consisting of borneol regarding dosage and medical indications. This study outlines the current state of research on the properties, formulation and pharmacological effects of borneol, allowing cross-comparison of borneol coupled with single compound and classical TCM formulas for various medical indications. This study aims to provide insights into the design of borneol-based enhanced cross-barrier delivery drug formulation, and the potential development of nano-drug system for TCM formulas with borneol for enhanced bioavailability.