Until a few decades ago , the oilseed crop for Perilla oil, from India, China and all across Eastern Asia was regarded as a species (P. ocymoides) in its own right, distinct from the "beefsteak plant" known for its red-leafed ornamental variety, although it was well established that these types readily cross-pollinate. Recent genetic research confirm they are of a common gene pool, corroborating the taxonomists' claim for consolidating the two crops into one species.
The red or purple leafed variety had been dubbed P. nankinensis, and this label was used throughout the 19th century in the West when it was introduced as an ornamental. (See under #English common names).
Whether green-leafed or red-leafed, the perillaldehyde factor that characterizes the unique shiso fragrance may turn out to be present or absent in the individual or population, and this is not differentiable from outward appearance alone. Chemical studies classify the genus into different chemotypes, depending on the essential oils they contain.
There are three wild species endemic to Japan, recognized as being genetically distinct fom the cultivated species. But some references treat, e.g., P. citrodora as the same species as the cultivated one
(= P. frutescens unless noted otherwise)
- Dentidia nankinensis Lour.
- Melissa maxima Ard. = P. frutescens
- Dentidia nankinensis Lour.
- Melissa maxima Ard.
- Mentha perilloides Lam.
- Mentha reticulosa Hance
- P. acuta (Thunb.) Nakai
- P. albiflora (Thunb.) Odashima
- P. arguta Benth.
- P. avium Dunn.
- P. crispa (Thunb.)
- P. cavaleriei H. Lév.
- P. nankinensis (Lour.) Decne
- P. ocymoides L.
- P. shimadai Kudo (in Journ. Soc. Trop. Agr. 3: 225. 1931)
- P. urticaefolia Salisb.
- Plectranthus nankinensis (Lour.) Spreng.
- Ocimum acutum Thunb.
- Ocimum crispum Thunb.
- Ocimum frutescens L.
Formerly placed here
- P. Elata D. Don. = Elsholtzia blanda Benth.
- P. fruticosa D. Don = Elsholtzia polystachya Benth. = E. frutiscosa (D. Don) Rehder
- P. leptostachya D. Don] = Elsholtzia incisa (Benth.) =? E. stachyodia" (Link)
- P. polystachya D. Don. = Pogostemon glabrum Willd.
The essential oil extracted from the leaves of perilla by steam distillation consists of a variety of chemical compounds, which may vary depending on species. The most abundant, comprising about 50–60% of the oil, is perillaldehyde which is most responsible for the aroma and taste of perilla. Other terpenes, such as limonene, caryophyllene, and farnesene, are common, as well.
Of the known chemotypes of perilla, PA (main component: perillaldehyde) is the only one used for culinary purposes. Other chemotypes are PK (perilla ketone), EK (eschscholzia ketone), PL (perillene), PP (phenylpropanoids: myristicin, dillapiole, elemicin), C (citral) and a type rich in rosefuran.
Perilla ketone is toxic to some animals. When cattle and horses consume purple mint (of the PK chemotype) while grazing in fields in which it grows, the perilla ketone causes pulmonary edema, leading to a condition sometimes called perilla mint toxicosis.
Perilla oil is obtained by pressing the seeds of perilla, which contain 35 to 45% oil. In parts of Asia, perilla oil used as an edible oil is valued more for its medicinal benefit than its flavor. Perilla oil is a very rich source of the omega-3 fatty acid alpha-linolenic acid. As a drying oil similar to tung oil or linseed oil, perilla oil has been used for paints, varnishes, linoleum, printing ink, lacquers, and for protective waterproof coatings on cloth. Perilla oil can also be used for fuel.
- 佐竹, 義輔 (Yoshisuke Satake); 西, 貞夫 (Sadao Nishi); 本山, 荻舟 (Tekishū Motoyama) (1969) , "しそ", 世界百科事典(Sekai hyakka jiten) (Heibonsha) 10: pp. 246–7 (world encyclopedia, in Japanese)
- e.g. 佐竹, 西 & 本山 1969 (Heibonsha encyclopedia), which classifies them as different species of the "same genus", and notes they hybridize easily
- Ito 2008, p.21, citing Ito et al., 1998
- Comprehensive study by Zeevart 1969 is often cited.
- See Yu, Kosuna & Haga 1997, p.2-3 for a sampling of this
- Yu, Kosuna & Haga 1997, p.2-3
- , "Ch. 2 Taxonomical Examination of Perilla Species and their revision – Studies on the Phylogenetic Relationship of the Species, p.20: "Japanese species 4 different species with 1 subspecies."
- Blaschek, Hänsel & Keller 1998, Hagers Handbuch, vol.3, p.328
- Bentham 1836,p.166
- Wiersema et al., "World Economic Plant: a standard reference (1999), p.160
- Rawayl & Pangtey, High Altitudes of the Himalaya: Biodiversity, ecology & environment (1994), p.338
- Bentham, George, biatarum genera et species: or, A description of the genera and species, p. 166, http://books.google.co.jp/books?id=uGhTAAAAYAAJ&pg=PA166
- Blaschek, Wolfgang; Hänsel, Rudolf; Keller, Konstantin (1998) (preview), Hagers Handbuch der Pharmazeutischen Praxis, 3 (L-Z), Gabler Wissenschaftsverlage, pp. 328-, ISBN 9783540616191, http://books.google.co.jp/books?id=XGXnVRiu3zoC&pg=PA328
- Ito, Michihiko (2008), "Studies on Perilla relating to its Essential Oil and Taxonomy" (preview), Phytochemistry research progress (Nova Publishers): pp. 13-, ISBN 9781604562323, http://books.google.co.jp/books?id=l5Mo0M5CqQcC&pg=PA22
- Yu, He-Ci; Kosuna, Kenichi; Haga, Megumi (1997) (preview), Perilla: the genus Perilla, Medicinal and aromatic plants--industrial profiles, 2, CRC Press, ISBN 9057021714, http://books.google.co.jp/books?id=M5A71gsWUskC
- Zeevaart, Jan A. D. (1969), L. T., ed., "Perilla spp.", The Induction of Flowering