Japanese honeysuckle

Japanese honeysuckle is a semi-evergreen twining vine 2–8 m tall (occasionally over 10 m), with round stems that are smooth or finely pubescent and often flushed red on one side; young shoots twine around supports. The opposite leaves are ovate to lanceolate-ovate or elliptic-lanceolate, 3–8 cm long, short-stalked, with smooth surfaces and small glands beneath. Flowers open in pairs from the leaf axils between May and July, with a five-toothed calyx and a two-lipped corolla — four lobes above, one below — white when they open and turning yellow after two to three days, so both colours appear together on one branch, the gold-and-silver pairing behind the Chinese name. The fruit is a glossy black berry 5–8 mm across, ripening in late summer.

According to Kew's Plants of the World Online the native range of Lonicera japonica is China to temperate eastern Asia, covering north-central, south-central and south-eastern China together with Japan, Korea, Manchuria and Taiwan. It is a deciduous to semi-evergreen plant of temperate and subtropical regions. The vine was introduced to Europe and North America from the early nineteenth century as an ornamental and is now regarded as invasive in many places (the United States, Australia, New Zealand and parts of Europe), where it mats over the ground, climbs and smothers native plants. In Vietnam it grows widely in thickets, forest margins, roadsides and hedgerows, typically up to about 1,500 m.

More than 140 compounds have so far been isolated from Japanese honeysuckle (Shang et al., Journal of Ethnopharmacology, 2011). The flowers are rich mainly in phenolic acids — chlorogenic acid (caffeoylquinic acid) together with 3,5-di-O-caffeoylquinic and 4,5-di-O-caffeoylquinic (isochlorogenic) acids — the principal quality markers. Key flavonoids include luteolin, luteolin-7-O-glucoside, chrysin and apigenin. A hallmark of the genus Lonicera is its secoiridoid glycosides such as sweroside, secologanin and loganin with their sucrose esters, accompanied by triterpenoid saponins. The Chinese Pharmacopoeia 2020 specifies that Lonicerae Japonicae Flos (buds or freshly opened flowers) must contain at least 1.5% chlorogenic acid, while premier growing regions reach 4–6%. Flower essential oil with β-caryophyllene, linalool and geraniol provides the light fragrance.

Lonicerae Japonicae Flos has been used for thousands of years in traditional Chinese medicine and is recognised in the Chinese Pharmacopoeia 2020 for clearing heat and detoxifying, indicated for wind-heat infections, fever, sore throat and eruptive fevers; research shows a range of anti-inflammatory, antibacterial, antiviral and antitumour effects. The systematic review by Zheng et al. (Frontiers in Pharmacology, 2022) confirms these activities of the flower, while Gao et al. (Molecules, 2026) review its food-medicine role and note that chlorogenic acid inhibits the NF-κB and MAPK pathways and reduces release of pro-inflammatory mediators such as IL-8. The flower is also brewed as honeysuckle tea, popular across China and East Asia, made into syrups and lozenges for sore throat, extracted for skincare cosmetics, and its secoiridoids and other secondary metabolites from the buds are under in-vitro study for anti-diabetic activity (Liu et al., Fitoterapia, 2016).

On safety, honeysuckle flower is cold in nature in traditional Chinese terms, so people with a cold-type deficiency of the spleen and stomach with chronic loose stools should use it cautiously, and prolonged high doses are best avoided in cold constitutions; rare reports of allergy and hypersensitivity to honeysuckle extract exist, so sensitive individuals should take note. An important point is distinguishing Lonicerae Japonicae Flos (Lonicera japonica) from Shan-yin-hua (Lonicera macranthoides and relatives) — the Chinese Pharmacopoeia separated the two groups after a review in 2015 over differing quality and activity. The ripe black berries are not recommended for eating. For conservation the species is Not Evaluated by the IUCN and is not in CITES; the medicinal supply depends on traditional growing areas such as Henan and Shandong in China, while in many countries outside the Old World it is instead controlled as an invasive plant.