Ocimum tenuiflorum

Ocimum tenuiflorum, commonly known as holy basil or tulsi or tulasi, is an aromatic perennial plant in the family Lamiaceae. It is native to tropical and subtropical regions of Australia, Malesia, Asia, and the western Pacific. It is widely cultivated throughout the Southeast Asian tropics. This plant has escaped from cultivation and has naturalized in many tropical regions of the Americas. It is an agricultural and environmental weed.

Tulasi is cultivated for religious and traditional medicine purposes, and also for its essential oil. It is widely used as an herbal tea, commonly used in Ayurveda, and has a place within the Vaishnava tradition of Hinduism, in which devotees perform worship involving holy basil plants or leaves.

Morphology
Holy basil is an erect, many-branched subshrub, 30-60 cm tall with hairy stems. Leaves are green or purple; they are simple, petioled, with an ovate blade up to 5 cm long, which usually has a slightly toothed margin; they are strongly scented and have a decussate phyllotaxy. The purplish flowers are placed in close whorls on elongated racemes.

The three main morphotypes cultivated in India and Nepal are Ram tulsi (the most common type, with broad bright green leaves that are slightly sweet), the less common purplish green-leaved (Krishna or Shyam tulsi) and the common wild vana tulsi (e.g., Ocimum gratissimum).

Phytochemicals
The plant and its oil contain diverse phytochemicals, including tannins, flavonoids, eugenol, caryophyllenes, carvacrol, linalool, camphor, and cinnamyl acetate, among others. One study reported that the plant contains an eponymous family of 10 neolignan compounds called tulsinol A-J.

Specific aroma compounds in the essential oil are camphor (32%), eucalyptol (19%), ⍺-bisabolene (17%), eugenol (14%), germacrene (11%) and β-bisabolene (11%). In addition, more than 60 different aroma compounds were found through gas chromatography–mass spectrometry analysis of holy basil. However, other studies have stated tulsi essential oil consists mostly of eugenol (70%) β-elemene (11%), β-caryophyllene (8%), and germacrene (2%), with the balance being made up of various trace compounds, mostly terpenes.

Culinary
Tulasi (Sanskrit: Surasa) has been used in Ayurvedic and Siddha practices for its supposed medicinal properties.

Thai cuisine
The leaves of holy basil, known as kaphrao in the Thai language (กะเพรา), are commonly used in Thai cuisine for certain stir-fries and curries such as phat kaphrao (ผัดกะเพรา) — a stir-fry of Thai holy basil with meats, seafood or, as in khao phat kraphao, with rice. Two different types of holy basil are used in Thailand, a "red" variant which tends to be more pungent, and a "white" version for seafood dishes. Kaphrao should not be confused with horapha (โหระพา), which is normally known as Thai basil, or with Thai lemon basil (maenglak; แมงลัก).

Insect repellent
For centuries, the dried leaves have been mixed with stored grains to repel insects.

Nematicidal
The essential oil may have nematicidal properties against Tylenchulus semipenetrans, Meloidogyne javanica, Anguina tritici, and Heterodera cajani.

Disinfection
Water disinfection using O. tenuiflorum extracts was tested by Bhattacharjee et al. 2013 and Sadul et al. 2009. Both found an alcoholic extract to be more effective than aqueous or leaf juice. Sundaramurthi et al 2012 finds the result to be safe to drink and antimicrobial. A constituent analysis by Sadul found alkaloids, steroids, and tannins in the aqueous, and alkaloids and steroids only in the alcoholic extract.

Significance in Hinduism
Tulasi is a sacred plant for Hindus, particularly the Vaishnavite sect. It is worshipped as the avatar of Lakshmi, and is often planted in courtyards of Hindu houses or temples to Hanuman. The ritual lighting of lamps each evening during Karthik includes the worship of the tulsi plant. Vaishnavites are also known as "those who bear the tulsi around the neck".

Tulasi Vivaha is a ceremonial festival performed between Prabodhini Ekadashi (the 11th or 12th lunar day of the bright fortnight of the Hindu month of Kartika) and Kartik Purnima (the full moon of the month).

Every evening, Bengali Hindus place earthen lamps in front of tulsi plants. During the Kati Bihu festival celebrated in Assam, people light earthen lamps (diya) at the foot of the household tulsi plants and pray.