Sea buckthorn berries consist of 23% seeds, 68% pulp, and 8% skin. The most valuable component of sea buckthorn fruits is their oil. There are two sources of oil in sea buckthorn fruit: seed oil and oil contained in the pulp of the fruit, quantitatively more compared to seed oil.

Both sea buckthorn seed oil and pulp oil have high total lipid content. The composition of sea buckthorn seed and pulp oils varies depending on the subspecies, origin, crop care activities, fruit harvesting time, and extraction method. The oil content of whole grains, pulp, and seeds of different sea buckthorn varieties in China: 45–84 g/kg in whole grains, 45–88 g/kg in the pulp, and 106–135 g/kg in the seeds. The yield of oil extraction differs depending on the drying method of the component parts of the fruit: 36% for sea buckthorn pulp dried in the air stream, compared to 16% for lyophilized pulp, while for seeds the values were similar: 11% and 12%, respectively.

The main constituents of neutral lipids in sea buckthorn are esters (esters of C20–C26 fatty acids with aliphatic alcohols), concentrated in the peel of the fruit and in the seed, C23–C29 hydrocarbons (most of the surface layer of the peel) and phytosterols (70–100% β-sitosterol, α- and β-amyrins, erythrodiol and other constituents of the unsaponifiable lipid fraction of seeds).

Sea buckthorn oil contains, on average, 35% palmitoleic acid, a rare and valuable acid, a component of skin fat, is known for its ability to support cell tissue and speed wound healing, as well as for hypocholesterolemic and hypotriglyceridemic actions. Sea buckthorn seed oil is characterized by a high content of oleic acid (17%) and a one-to-one ratio of omega-3 (alpha-linolenic) and omega-6 (linoleic) at about 34% and 31%, respectively. The equivalence relationship between the two omegas is particularly important, intervening in the regulation of thousands of metabolic functions. Almost every biological function is interconnected with the balance between omega-6 and omega-3.

Sea buckthorn seed oil and sea buckthorn pulp oil differ considerably in the composition of fatty acids. Saturated fatty acids are found in sea buckthorn pulp oil, mainly palmitic acid, while sea buckthorn seed oil contains C18 type unsaturated fatty acids, such as linoleic acid (18:2) and linolenic acid (18:3). In sea buckthorn pulp oil, the main fatty acids identified were palmitoleic acid (16:1n-7), palmitic acid (16:0), and oleic acid.

After studying the fatty acid composition of oils from the pulp/peel, seeds, and whole fruits of sea buckthorn varieties in Tibet, Gansu, and Shanxi, and also the oil content of the seeds, pulp/peel, and whole sea buckthorn fruits (based on fresh weight). The oil quantities from different parts of sea buckthorn fruit varied as follows: 45–84 g oil/kg whole berries, 45–88 g oil/kg sea buckthorn pulp/peel, 106–135 g oil/kg sea buckthorn seeds. Due to the predominance of pulp and peel in sea buckthorn fruit, the composition of whole fruit oil is similar to that of pulp/peel oil. The levels of fatty acids in seed oil and in sea buckthorn peel varied greatly between the studied varieties.

The predominant fatty acids in the oils from sea buckthorn pulp/peel were palmitic (23–40%), oleic (20–53%), and palmitoleic (11–27%). Small amounts or traces of vaccenic acid, linoleic acid, α-linolenic acid, stearic acid, myristic acid, pentadecanoic acid, cis-7 hexadecanoic acid, margaric acid, and two long-chain fatty acids, arachidic acid and eicosanoic acid were detected in all oils from the soft parts of the sea buckthorn fruit. Monounsaturated fatty acids are the most important class of fatty acids in terms of quantity (53–70%), followed by saturated fatty acids (26–41%), and then polyunsaturated fatty acids (3–7%).

Similar amounts of palmitic acid, vaccenic acid, and α-linolenic acid have been reported for sea buckthorn pulp oils in the Indian summer variety and, H. rhamnoides. Higher proportions of palmitoleic acid and much lower levels of oleic acid are characteristic of sea buckthorn pulp oils from subspecies in Finland and Canada.

Sea buckthorn seed oil contains mainly the following acids: linoleic, α-linolenic, oleic, palmitic, and stearic, with small amounts or traces of vaccenic, palmitoleic, arachidic, eicosanoic, myristic, pentadecanoic, and margaric acid. A notable feature of sea buckthorn seed oil is the extremely low level of palmitoleic acid (0.1–0.5%). Large relative deviations were observed for oleic acid (13–21%) and linoleic acid (33–43%) concentrations. Unlike pulp oil, sea buckthorn seed oil had higher amounts of polyunsaturated fatty acids (65–72%) and lower amounts of monounsaturated fatty acids (16–21.5%) and saturated fatty acids (11–16%), respectively.

Sea buckthorn pulp/peel contains high content of palmitoleic acid, which forms a large part of the epidermal lipids of human skin therefore the pulp oil of sea buckthorn is often used in cosmetics emulsion. Many studies on palmitoleic acid have focused on the health of the skin and mucous membranes, based on the fact that omega-7 is present in both body structures.

Additionally, sea buckthorn is a very good source of phytosterols, which play an important role in the prophylaxis of cardiovascular diseases induced by hypercholesterolemia. Sitosterol has recently been intensively investigated for its physiologically beneficial effects on humans and is associated with a reduction in cancer incidence.

Phytosterols are the main constituents of the unsaponifiable fraction of sea buckthorn oils. The sterol content in sea buckthorn berries is from 2.2 to 8.8%. At least 17 types of sterols have been identified in the sea buckthorn, of which β-sitosterol is quantitatively the most important.

The total sterol content in sea buckthorn seed oil varies from 12 g/kg to 23 g/kg, in soft parts between 10 g/kg and 29 g/kg, and in the whole fruit, the variation range is between 13 g/kg and 33 g/kg. Sitosterol represents 57–76% of total sterols in seeds and 61–83% of total sterols in soft parts.

The most important phytosterols in seeds are δ-5-Avenasterol and obtusifoliol (approx. 15–17% of total sterols) and together with stigmasta-8-ene-3β-ol are about 5–6 and 8–10% of total sterols from soft parts and whole fruits, respectively.

Sea buckthorn is a better source of β-sitosterol than other very popular oils such as soybean oil, and the total amount of phytosterols in sea buckthorn exceeds 4 to 20 times the amount in soybean oil. Therefore, sea buckthorn is obviously worthy of being considered a source of phytosterols in the diet.