Sea-buckthorn (Hippophae rhamnoides), also known as sea buckthorn, sandthorn, sallowthorn or seaberry, is a species of flowering plant in the family Elaeagnaceae, native to cold-temperate regions of Eurasia. It is a spiny deciduous shrub. The fruit has culinary uses, while its extracts, including its oil, are used in the cosmetics industry and within traditional medicine. It is also used as animal fodder, in horticulture, and for ecological purposes.
Description and biology
Sea-buckthorn is a hardy, deciduous suckering shrub that can grow between 2–5 metres (6 ft 7 in – 16 ft 5 in) high, rarely 15 m (49 ft), forming extensive clonal colonies by root sprouts. It has rough, brown or black bark and a thick crown of greyish-green foliage. Like many species of the family Elaeagnaceae, the young shoots and leaves are covered in small silvery scales. The leaves are alternate, narrow and lanceolate, 1–8 cm long and up to 1 cm broad with silvery-green surfaces at first; the upper side darkens to mid to dark grey-green through the summer as the scales wear off, while the underside remains silvery. It is dioecious, with male and female flowers growing on different shrubs. The sex of seedlings can only be determined at the first flowering, which mostly occurs after three years. The male inflorescence is built up of four to six apetalous flowers, while the female inflorescence normally consists of only one apetalous flower and contains one ovary and one ovule. Fertilisation occurs solely via wind pollination, so male plants need to be close to female plants to allow for fertilisation and fruit production. The globose to oval fruit are 6–8 mm diameter, grow in compact dense clusters, and are typically bright orange, but vary from pale yellow to dark orange. The individual fruit weigh between 270 and 480 mg. The plants have a developed and extensive root system, and the roots live in symbiosis with nitrogen-fixing Frankia bacteria. The roots also transform insoluble organic and mineral matters from the soil into more soluble states. Vegetative reproduction of the plants occurs rapidly via root suckers.
Fruit
The fruit contains sugars, sugar alcohols, fruit acids, vitamins, polyphenols, carotenoids, fibre, amino acids, minerals, and plant sterols. Species belonging to genus Hippophae accumulate oil both in the pulp and in seed of the fruit. Oil content in the pulp is 1.5–3.0%, while in seeds, oil is 11% of the fresh weight. Major sugars in sea-buckthorn fruit are fructose and glucose, with total sugar content of 2.7–5.3 g/100 ml of juice. The typical sourness of the fruit is due to high content of malic acid (0.8–3.2 g/100 ml of juice) while astringency is related to quinic acid (1.2–2.1 g/100 ml of juice). Major sugar alcohol in fruit is L-quebrachitol (0.15–0.24 g/100 ml of juice).
Phytochemicals The fruit is rich in phytosterols (340–520 mg/kg), β-sitosterol being the major sterol compound as it constitutes 57–83% of total sterols. Flavonols were found to be the predominating class of phenolic compounds, while phenolic acids and flavan-3-ols (catechins) represent minor components.
Taxonomy Hippophae rhamnoides is in the family Elaeagnaceae in the order Rosales.
Subspecies Seven subspecies are accepted, with three in Europe and four more in Asia. The subspecies vary in size, shape, number of main lateral veins in the leaves and quantity and colour of stellate hairs. The central Asian subspecies grow much taller; the European subsp. rhamnoides only reaches 5 m, but the Chinese subspecies are reported to reach 15 m to even 18 m tall.
Hippophae rhamnoides subsp. carpatica Rousi — Carpathian Mountains in central and eastern Europe Hippophae rhamnoides subsp. caucasica Rousi — southeastern Europe (Bulgaria), southwestern Asia in Iran, Turkey and the Caucasus Mountains Hippophae rhamnoides subsp. mongolica Rousi — east-central Asia Hippophae rhamnoides subsp. rhamnoides — northern & western Europe Hippophae rhamnoides subsp. turkestanica Rousi — west-central Asia Hippophae rhamnoides subsp. wolongensis Y.S.Lian, K.Sun & X.L.Chen — central China Hippophae rhamnoides subsp. yunnanensis Rousi — southwestern China, Tibet An eighth subspecies Hippophae rhamnoides subsp. fluviatilis Soest is accepted by the Euro+Med-Plantbase, but treated by POWO as a synonym of nominate subsp. rhamnoides. This is claimed to have fewer thorns than other subspecies, and is used for breeding, due to easier harvesting methods.
Etymology The genus name Hippophae comes from Ancient Greek ἵππος (híppos), meaning 'horse', and φάος (pháos), meaning 'light', and is due to the ancient Greeks use of sea-buckthorn leaves as horse fodder to make their coats shine more. The specific epithet rhamnoides derives from Rhamnus plus -oides, resembling, referring to the superficial similarity to the buckthorn genus Rhamnus.
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