(Lour.) Soják 1974
Polygonum odoratum Lour. 1790
Persicaria odorata, with common names Vietnamese coriander, Vietnamese cilantro, phak phai, hot mint and Cambodian mint, is a herb whose leaves are used in Southeast Asian and Northeast Indian cooking.
Vietnamese coriander is not related to the mints, nor is it in the mint family Lamiaceae, but its general appearance and fragrance are reminiscent of them. Persicaria is in the family Polygonaceae, collectively known as "smartweeds" or "pinkweeds".
The leaves are locally known as phak phai in Manipur. The Khoibu community grind the leaves with ghost pepper and a nut locally known as "bonra" to make a spicy side dish.
Above all, the leaf is identified with Vietnamese cuisine, where it is commonly eaten fresh in salads (including chicken salad) and in raw gỏi cuốn, as well as in some soups such as canh chua and bún thang, and stews, such as fish kho tộ. It is also popularly eaten with hột vịt lộn (fertilized duck egg).
In the cuisine of Cambodia, the leaf is known as (Khmer: ជីរក្រសាំងទំហំ chi krasang tomhom) and is used in soups, stews, salads, and the Cambodian summer rolls, naem (ណែម).
In Singapore and Malaysia, the shredded leaf is an essential ingredient of laksa, a spicy noodle soup, so much so that leaf is commonly referred to as "laksa leaf". The Malays called the leaves 'daun kesum' and is used in Malaysia for the dishes nasi kerabu and asam pedas.
In Laos and certain parts of Thailand, the leaf is eaten with raw beef larb (Lao: ລາບ).
In Australia, the plant is being investigated as a source of essential oil (kesom oil).
The Vietnamese coriander is a perennial plant that grows best in tropical and subtropical zones in warm and damp conditions. In advantageous conditions, it can grow up to 15–30 cm (6–12 in). The top of its leaf is dark green, with chestnut-colored spots, while the leaf's bottom is burgundy red. The stem is jointed at each leaf. In Vietnam, it can be cultivated or found in the wild. It can grow very well outside in summer in nontropical Europe. It prefers full sun and well-drained soil. For colder climate zones, they should be brought inside for the winter and treated as a house plant. For climate zones that have milder winters, they will survive outside, although their growth may slow down. It rarely flowers outside the tropics.
Its oil contains aldehydes such as decanal (28%), and the alcohols dodecanol (44%) and decanol (11%). Sesquiterpenes such as α-humulene and β-caryophyllene comprise about 15% of its oil.
C-Methylated homoisoflavanones (3-(4'-methoxy-benzyl)-5,7-dihydroxy-6-methyl-8-methoxy-chroman-4-one, 3-(4'-methoxy-benzyl)-5,7-dihydroxy-6,8-dimethyl-chroman-4-one, 3-(4'-hydroxy-benzyl)-5,7-dihydroxy-6,8-dimethyl-chroman-4-one, 3-(4'-hydroxy-benzyl)-5,7-dihydroxy-6-methyl-8-methoxy-chroman-4-one and 3-(4'-hydroxy-benzyl)-5,7-dihydroxy-6-methyl-chroman-4-one) can be found in the rhizomes of P. odoratum.
No scientific studies have measured P. odorata's effects on libido. Traditionally, in Vietnam, the herb is believed to repress sexual urges. A saying in Vietnamese states, "rau răm, giá sống" ("Vietnamese coriander, raw bean sprouts"), which refers to the common belief that Vietnamese coriander reduces sexual desire, while bean sprouts have the opposite effect. Many Buddhist monks grow coriander in their private gardens and eat it frequently, believing it helps them remain celibate.