Lonicera japonica

The Japanese honeysuckle (Lonicera japonica; Suikazura スイカズラ／吸い葛 in Japanese; Jinyinhua in Chinese; 忍冬 in Chinese and Japanese) is a species of honeysuckle native to eastern Asia including China, Japan and Korea. It is a twining vine able to climb up to 10 m high or more in trees, with opposite, simple oval leaves 3 – long and 2 – broad. The flowers are double-tongued, opening white and fading to yellow, and sweetly vanilla scented. The fruit is a globose dark blue berry 5 – diameter containing numerous seeds.

It is an invasive species in a number of countries.

Cultivation and uses
This species is often sold by American nurseries as the cultivar 'Hall's Prolific' (Lonicera japonica var. halliana). It is an effective groundcover, and has pleasant, strong-smelling flowers. It can be cultivated by seed, cuttings, or layering. In addition, it will spread itself via shoots if given enough space to grow.

In both its native and introduced range, Japanese honeysuckle can be a significant source of food for deer, rabbits, hummingbirds and other wildlife.

The variety L. japonica var. repens has gained the Royal Horticultural Society's Award of Garden Merit.

Invasive species
Japanese honeysuckle has become naturalized in Argentina, Australia, Brazil, Mexico, New Zealand and much of the US, including Hawaii, as well as a number of Pacific and Caribbean islands.

In the US, Japanese honeysuckle is classified as a noxious weed in Texas, Illinois, and Virginia, and is banned in New Hampshire. It grows extremely rapidly in parts of America such as southwestern Ohio and is virtually impossible to control in naturalized woodland edge zones due to its rapid spread via tiny fruit seeds. It forms a tall dense woody shrub layer that aggressively displaces native plants. It is also very difficult to manage in semi-wild areas, such as in large rural yards.

It is listed on the New Zealand National Pest Plant Accord as an unwanted organism.

It can be controlled to some degree via labor-intensive methods such as cutting or burning the plant to root level and repeating at two-week intervals until nutrient reserves in the roots are depleted. It can also be controlled through annual applications of glyphosate, or through grubbing if high labor and soil destruction are not of concern. Cutting the honeysuckle to within 5–10 cm of the ground and then applying glyphosate has proven to be more effective, provided that the mixture is rather concentrated (20–25%) and is applied immediately after making the cut.

Chinese medicine
The Japanese honeysuckle flower is of high medicinal value in traditional Chinese medicine, where it is called rěn dōng téng (literally "winter enduring vine" ) or jīn yín huā (literally "gold silver flower"). Alternative Chinese names include er hua and shuang hua. In Korean, it is called geumeunhwa. The dried leaves are also used in traditional Chinese medicine.

Jin Yin Hua (Japanese Honeysuckle, Flos Lonicerae Japonicae) is notable for its inclusion in the traditional Chinese medicine herbal formula Honeysuckle and Forsythia Powder. In pinyin, this formula is called Yin Qiao San. Traditional indications for use of this formula include fever, headache, cough, thirst, and sore throat. For indications such as this, it is common to find Japanese Honeysuckle paired in Chinese medicine herbal formulations with Forsythia (Lian Qiao, Fructus Forsythiae Suspensae). According to Chinese medicine, these herbs, when combined, have a synergistic medicinal effect to address indications such as fever with headache and sore throat. This is why these two herbs are considered "paired herbs".

In Chinese medicine, Jin Yin Hua is classfied with a temperature property of cold. The cold designation specifically refers to, in this case, to Jin Yin Hua's antitoxin, anti-bacterial, antipyretic, and anti-inflammatory properties. Also, according to traditional Chinese medicine, Jin Yin Hua is contraindicated for patients with medical conditions that are diagnosed as deficient and cold in nature unless combined with other herbs to balance the temperature nature of Jin Yin Hua. In layperson terms, Jin Yin Hua is used in Chinese medicine to address what are called excess heat conditions such as fevers, skin rashes, and sore throat. Excess heat conditions are essentially inflammatory processes involving heat, redness, pain, and swelling often due to external pathogenic factors such as bacteria and viruses. The cold nature of Jin Yin Hua is considered to cool the heat nature of the heat related conditions. For example, Jin Yin Hua's antibacterial properties can help to cool a fever. In this case, the cold herb treats the heat condition. However, should a patient present with what is termed as a cold condition such as aversion to cold with cold limbs, cold and pain in the abdomen, and abdominal pain relieved by warmth, then Jin Yin Hua's cold nature is said to be contraindicated for treating the pre-existing cold condition. Should an herbalist choose to use Jin Yin Hua in an herbal formula for a patient with a cold condition, he/she would then choose to balance the temperature of Jin Yin Hua with another herb that is warming in nature.

Chemistry
Lonicera japonica contains methyl caffeate, 3,4-di-O-caffeoylquinic acid, methyl 3,4-di-O-caffeoylquinate, protocatechuic acid, methyl chlorogenic acid and luteolin. These compounds have an inhibitory effect on human platelet aggregation that may explain the possible role of Japanese honeysuckle in maintaining vascular homeostasis. The two biflavonoids, 3′-O-methyl loniflavone (5,5″,7,7″-tetrahydroxy 3′-methoxy 4′,4‴-biflavonyl ether) and loniflavone (5,5″,7,7″,3′-pentahydroxy 4′,4‴-biflavonyl ether) along with luteolin and chrysin can be isolated from the leaves. Other phenolic compounds present in the plant are hyperoside, chlorogenic acid and caffeic acid.

The two secoiridoid glycosides, loniceracetalides A and B, can be isolated, together with 10 known iridoid glycosides, from the flower buds.

The plant also contains the saponins loniceroside A and B and the antiinflammatory loniceroside C.