Black seed oil extracted from black seeds is obtained from Nigella sativa plant. In Ayurveda (The Indian Medicinal system), black seed preparations are in use for several therapeutic purposes such as astringent (topical application helps to skin pore constriction), bitter (detoxify body), stimulant (enhance energy level), diuretic (increase urine secretion), emmenagogue (increase menstrual bleeding), anthelmintic (worm destruction from gut), jaundice (liver disorder), fever, indigestion, piles, skin diseases and paralysis.  It is amazing to know that a self-branching bushy Nigella sativa plant can be such a versatile source for multiple health benefits. Several pharmacognostic researches showed that the used part of a medicinal plant for therapeutic purposes contain several natural chemical substances, which are termed as phytochemicals. Therefore, it is imperative to know which phytochemicals in black seed oil are present before incorporating it into the modern medicinal system.
Several studies have been performed to analyze the composition of the black seed. The result showed that fixed oil, essential volatile oil, alkaloid, protein, and saponin are the constituents present in black seeds. An extensive report from study result provided a detailed composition of each constituent. 
The fixed oil obtained from black seed is almost 30% to 40 % and the constituents present in fixed oil are arachidonic, almitoleic, eicosadienoic, linoleic, linolenic, myristic, oleic, palmitic and stearic acid. Other constituents present are beta-sitosterol, cycloartenol, cycloeucalenol, sterol esters and sterol glucosides.
Essential Volatile Oil
The amount of essential volatile oil obtained from black seeds varies from 0.4% to 0.45 %.The only saturated fatty acid which contains a component of the carbonyl fraction is nigellone. The primary constituent of volatile oil which is the most potent therapeutic constituent obtained from black seeds is Thymoquinone (TQ), a quinone derivative. Other quinone derivatives that possess therapeutic benefits are thymohydroquinone (THQ), dithymoquinone, thymol, α and β-pinene, carvacrol, d-citronellol, d-limonene, p-cymene, longifoline, t-anethole, and 4-terpineol. The total volatile oil obtained from Black seed are composed of almost 54% of Thymoquinone. Some amount of Thymoquinone gets converted to dithymoquinone in exposure to sunlight during storage and extraction process. 
Both fixed oil and volatile oil are rich in proteins, amino acids, unsaturated fatty acids, traces of alkaloids and terpenoids. 
Two different kinds of alkaloids present in Black seeds are isoquinoline alkaloid and pyrazol alkaloid. Critical phytochemical analysis showed nigellicimine, nigellicimine n-oxide are isoquinoline alkaloid, whereas nigellidine and nigellicine are pyrazol alkaloids specifically present in the Black seed.
Back seed also contains saponin and alpha hederine. Other trace materials found in Black seeds are carvone, citronellol, and limonene. 
Black seeds have some important nutritional components such as carbohydrate, protein, essential amino acids, fats, and crude fibers. A significant amount of vitamins and minerals like calcium, iron, potassium, zinc, copper and phosphorus are also present in Black seeds. Carotene, present in Black seed gets converted to vitamin A through liver metabolism. 
Therapeutic Benefits from Phytochemicals present in Black seed
All these phytochemicals provide different therapeutic benefits; like Saponin has potential effect against cancer development. Flavonoids and Vitamin E present in black seed act against liver dysfunction. Nigellone and thymoquinone have significant blood glucose lowering effect by stimulating insulin secretion in type 2 diabetic patients. Antioxidant properties are due to thymoquinone, carvacrol, t-anethole, and 4-terpineol. The strong antioxidant property of thymoquinone helps to act against nephrotoxicity, cardiotoxicity and also act as a hepatoprotector.  Other promising therapeutic effects of thymoquinone present in black seed oil are anticonvulsant activity, anti-inflammatory, anti-cancer, antibacterial and antifungal activity. There are varieties of Black seed depending upon the specific origin of location and the concentration of chemical constituents in Black seed oil depends upon their origin and process through which oil extraction followed. 
- Haseena S, ManjunathAithal, Kusal K Das, Shaik Hussain Saheb; Phytochemical Analysis of Nigella sativa and its Effect on Reproductive System; J. Pharm. Sci. & Res. Vol. 7(8), 2015, 514-517; Online available at http://jpsr.pharmainfo.in/Documents/Volumes/vol7Issue08/jpsr07081503.pdf
- FatemehForouzanfar, Bibi SedighehFazlyBazzaz, Hossein Hosseinzadeh; Black cumin (Nigella sativa) and its constituent (thymoquinone): a review on antimicrobial effects; Iran J Basic Med Sci.2014 Dec; 17(12): 929–938; Online available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4387228/
- Desai S D, Shaik Hussain Saheb, Kusal K Das, Haseena S; Phytochemical Analysis of Nigella sativa and it`s Antidiabetic Effect; J. Pharm. Sci. & Res. Vol. 7(8), 2015, 527-532; Online available at http://jpsr.pharmainfo.in/Documents/Volumes/vol7Issue08/jpsr07081506.pdf
- Said Gharby, Hicham Harhar, Dominique Guillaume, Aziza Roudani, Samira Boulbaroud, Mohamed Ibrahimi, Mushtaq Ahmad, Shazia Sultana, Taibi Ben Hadda, Imane Chafchaouni-Moussaoui, Zoubida Charrouf; Chemical investigation of Nigella sativa L. seed oil produced in Morocco; Journal of the Saudi Society of Agricultural Sciences; Volume 14, Issue 2, June 2015, Pages 172–177; Online available at http://www.sciencedirect.com/science/article/pii/S1658077X13000507