Comparison of pharmacological activity and safety of different stereochemical configurations of borneol: L-borneol, D-borneol, and synthetic borneol

Background: Chiral drugs generally exhibit differences in activity because they bind differently to their target receptor. The Chinese medicine borneol ('Bing Pian' in Chinese) is a bicyclic monoterpenoid with a wide range of biological activities. Three kinds of Chinese medicines comprising borneol are used clinically, namely, L-Bor-neolum ('Ai Pian' in Chinese), Borneolum ('Tian Ran Bing Pian' in Chinese), and synthetic borneol ('He Cheng Bing Pian' in Chinese). The three kinds of borneol have different stereochemical configurations, but their clinical uses are nearly identical, and their prices vary widely. However, there is no clear rational basis for the selection of these kinds of borneol in clinical applications. Purpose: The purpose of this study was to clarify differences in the biological activity, safety, and structure-activity relationship of the three kinds of borneol. Methods: 'borneol', 'Bing Pian', 'Ai Pian', 'Tian Ran Bing Pian', and 'He Cheng Bing Pian' were selected as keywords to search for and extract relevant literature in the CNKI, PubMed, and Google Scholar databases up to November 2022. Results: L-borneol has better potential in cerebrovascular diseases. The three kinds of borneol have stronger penetration-promoting effects on hydrophilic drugs. L-borneol and isoborneol promote intestinal mucosal absorption of drugs via bidirectional regulation of P-glycoprotein. D-borneol exhibits better antitumour sensitizing effects than L-borneol. L-borneol exhibits better inhibition of bacterial adhesion because of its C2 chiral centre. Synthetic borneol is less safe. Conclusion: L-borneol has excellent potential in many aspects, has various sources, and can effectively replace expensive D-borneol in some applications.