Phytochemistry and Pharmacological Evidence of East Asian Crowberry Reported as Empetrum nigrum var. japonicum or E. nigrum subsp. asiaticum: A Critical Review of Potential Chemotypic Differentiation

East Asian crowberry has been reported under Empetrum nigrum var. japonicum and E. nigrum subsp. asiaticum. This critical narrative review evaluates taxonomy, phytochemistry, and pharmacological evidence from Korean, Japanese, and Chinese source-reported material in the context of the wider Empetrum literature. Reassessment of primary reports identified a broader East Asian chemical evidence base than previously summarized, including methylated, methoxylated, and hydroxylated chalcone/dihydrochalcone derivatives, bibenzyls, triterpenoids, flavonoids, and related constituents. These reports raise the possibility of East Asian chemotypic differentiation, but direct comparative metabolomics using authenticated populations and standardized methods has not established their geographic specificity or abundance. Reported pharmacological activities include antioxidant and cytoprotective effects, nitric oxide and α-glucosidase inhibition, cancer cell cytotoxicity, anti-angiogenic activity in an in ovo chorioallantoic membrane model, and limited mammalian in vivo evidence, including a Korean carbon tetrachloride-induced hepatotoxicity model and a Chinese alcoholic fatty liver rat model. Evidence strength varies substantially because botanical authentication, extract standardization, dose–response reporting, and independent replication are inconsistent. The available literature therefore provides preliminary evidence consistent with potential East Asian chemotypic differentiation but does not establish a discrete chemotypic boundary. Priority needs are taxonomic authentication, harmonized chemical profiling, quantitative marker validation, extract standardization, compound-level testing, and independent pharmacological replication.