Perilla

Perilla is an annual herb 0.3–1.5 m tall with a square, branched stem, green or purple. Leaves are opposite and stalked, broadly ovate to almost round, 5–13 cm long and 3–10 cm wide, with deep teeth or crisped margins; in the purple form the colour comes from anthocyanins. The inflorescence is a lax one-sided raceme with two flowers per whorl; the bell-shaped calyx is 3 mm in flower and enlarges to 11 mm in fruit, two-lipped; the corolla is 3–4 mm with five nearly equal lobes and four spreading stamens. The fruit is a small pale-brown schizocarp with one to four seeds.

According to Kew's Plants of the World Online, the native range of perilla runs from the southern Russian Far East (Primorye, Khabarovsk) through East Asia to Pakistan — including China (many southern and south-western provinces), Japan, Korea, Taiwan, the East Himalaya, India, Nepal, Bhutan, Bangladesh, Myanmar, Thailand, Laos, Vietnam and Java. The species favours subtropical habitats and grows in moist disturbed ground, roadsides, waste places and gardens. It has been introduced and naturalised in parts of Europe, southern European Russia, Ukraine, Romania, the eastern United States and Ontario (Canada), where it is often treated as a weed. In Vietnam perilla is grown around homes and readily self-seeds.

Perilla is a chemically rich plant: a review in Molecules (2022) catalogued about 400 bioactive compounds in the leaves, stems, roots and seeds — alkaloids, terpenoids, quinones, phenylpropanoids, flavonoids, coumarins, anthocyanins, carotenoids, neolignans and fatty acids. The leaf essential oil is defined by perillaldehyde (the monoterpene aldehyde behind the anise–cool aroma) in the PA chemotype, together with perilla ketone, limonene, perillene and linalool. The main phenolics are rosmarinic acid (quantified by HPLC in leaf extract at about 33 mg/g, the most abundant key compound), caffeic acid, scutellarin, luteolin and luteolin-7-O-glucoside, quercetin, apigenin and a potent anti-allergic methoxyflavanone (8-hydroxy-5,7-dimethoxyflavanone). Purple leaves are also rich in the anthocyanins that supply their colour, while the seeds yield an oil more than half of which is α-linolenic acid (omega-3).

Perilla's most notable clinical research centres on rosmarinic acid. A randomised, double-blind, placebo-controlled trial by Takano et al. (Experimental Biology and Medicine, 2004) in 29 people with seasonal allergic rhinitis showed that a rosmarinic-acid-rich extract (50 or 200 mg/day for 21 days) significantly raised responder rates for itchy nose, watery and itchy eyes and reduced neutrophils and eosinophils in nasal lavage fluid. In the same year Osakabe et al. (BioFactors, 2004) and Sanbongi et al. (Clinical and Experimental Allergy, 2004) showed that rosmarinic acid suppresses allergic inflammation and house-dust-mite lung inflammation in mouse models. A clinical review on PubMed Central (2023) reported that perilla-containing preparations cut the total seasonal allergic-rhinitis symptom score by up to 37% as an add-on to standard therapy, and a 2023 network-pharmacology study identified the MAPK pathway as the main mechanism of perilla leaf against allergic asthma. In practice the leaves are eaten as a raw herb and used as a diaphoretic medicine (colds, coughs, indigestion), while the seeds (zi su zi) enter cough–asthma formulas and are pressed for omega-3-rich oil.

As to safety, perilla is used as a food at culinary doses and is generally considered safe; clinical trials with rosmarinic-acid-rich extracts reported no serious adverse effects. Caution is nonetheless warranted with large amounts or concentrated essential oil: some chemotypes contain perilla ketone, and World Flora Online warns that large doses can cause pulmonary oedema (documented in livestock), so pregnant women and people on anticoagulants should seek medical advice before high-dose use. The species is not globally threatened: its native range stretches from the Russian Far East to Pakistan and it is widely cultivated and naturalised, so genetic resources are ample; conservation mainly means maintaining local forms (purple, green, white) and clean seed stocks.