Download PDF
Mentha ×piperita L.
Standardized Common
Name: Peppermint
Family: Lamiaceae (Labiatae)
Taxonomy: The genus Mentha
includes about two dozen species of aromatic herbs. Its taxonomy is complicated
by frequent hybridization in section Mentha and the existence of
numerous cultivated forms. Most hybrids are sterile or nearly so and are
propagated vegetatively. M. ×piperita is a sterile hybrid of M.
aquatica L. (Water Mint) and M. spicata L. (Spearmint, itself
believed to have originated as a hybrid of two other species). Several
peppermint cultivars have distinctive chemical content and flavor; one of
these, Lemon Mint, is sometimes treated as a separate species (M. citrata
Ehrh.).
Description: Perennial herb, 30–100
cm high, with aerial stems arising from creeping rhizomes, erect or partially
trailing and sometimes rooting at nodes. Stems quadrangular, branching,
purplish, usually glabrous or nearly so, rarely tomentose. Leaves opposite,
petiolate, 1–9 cm long, lanceolate to lanceolate-oblong, ovate-oblong or rarely
ovate; base rounded to cuneate or subcordate; apex acute; margins serrate. Inflorescence
a terminal spike formed of closely spaced verticillasters, the lowermost whorl
or whorls usually separate; bracts 4–7 mm long. Calyx ca. 3 mm long, 5-toothed,
bearing glands; teeth narrowly triangular with ciliate margins. Corolla pink to
lavender or purple, 3–3.5(–4.0) mm long, weakly bilabiate, 4-lobed. Stamens 4,
all of similar length. Ovary 4-lobed; style divided in two at apex, protruding
from corolla. Fruit 4 nutlets, 0.5–0.7 mm long, not viable.
Parts
in Commerce:
Leaves, sometimes with flowering tops
Identification:
Leaves
and stems
- Stem fragments
quadrangular, light green to purple (stems over a certain size, usually 1
mm or 3 mm in diameter, are limited to a minimal quantity according to
most specifications)
- Stems hairless
or with very sparse pubescence (rarely, wild European populations are
hairy)
- Leaf blade (1–)2–7(–9)
cm long, lanceolate to ovate-oblong, green or purplish
- Always
petiolate; petioles 4–15 mm long (shorter on smallest leaves), glabrous or
slightly pubescent
- Base rounded to
cuneate or very shallowly cordate, sometimes asymmetrical
- Apex acute to narrowly
acute
- Margins serrate;
teeth sharp, shallow, often somewhat uneven, not at all bent outward
- Venation
pinnate, often purple-tinged beneath
- Round yellowish
glands numerous on lower surface
- Non-glandular
hairs very sparse, occuring mostly along veins on lower surface (except in
rare wild European populations)
- Dried leaves
brittle and often crumpled
- Odor
characteristic, aromatic
- Taste
characteristic, pungent, producing a cool sensation
Flowering
tops
- Terminal spike,
3–7 cm long, formed of closely spaced verticillate whorls of flowers; gap
between lowermost two whorls usually larger
- Bracts narrow,
leaflike, longer than flowers
- Calyx ca. 3 mm
long, campanulate, with 5 ciliate-margined lobes, green to purple, bearing
glands
- Corolla 3.0–3.5(–4.0)
mm long, 4-lobed, tubular-campanulate, slightly bilabiate, pink to purple
- Stamens 4
- Nutlets 4 per
flower, 0.5–0.7 mm long
Adulterants: Chinese Mint (aka
Japanese or Brazilian peppermint, M. canadensis L.) has recently
appeared as an adulterant of M. ×piperita. It is referred to as M.
arvensis L. var. piperascens Malinv. ex Holmes in some literature,
but M. canadensis has been shown to
be a distinct species, probably an ancient hybrid of the European M. arvensis and M. longifolia (L.) L. The Asian variety contains menthol and has a
taste similar to that of peppermint; North American M. canadensis is chemically distinct and does not contain
significant menthol. Wichtl suggests that Asian M. canadensis is most
easily identified by its lack of menthofuran in TLC analyses, as it is
morphologically very similar to M. ×piperita. The best means of
distinguishing sterile material is that the stem angles of M. arvensis
are pubescent, sometimes densely, and the remainder of the stem may also be
pubescent. The leaves are sometimes broadly ovate or elliptical, and the upper
surfaces may bear soft weak pubescence. Leaf teeth may be blunt and few in
number, although in Asian material they are usually similar to those of M. ×piperita.
Flowers are borne in separated whorls instead of a spike. The corolla is
slightly pubescent inside, and is sometimes white.
Spearmint
(M. spicata) is a formerly reported adulterant that lacks menthol and
therefore does not have the strongly cooling taste of genuine peppermint. The
leaves and stems are sometimes pubescent.
References:
Fernald ML, Gray’s
Manual of Botany, 8th ed. New York: American Book Company; 1950: 1247–1250.
Gobert V, Moha S, Colson M, Taberlet P. Hybridization
in the section Mentha (Lamiaceae) inferred from AFLP markers. Amer J
Bot. 2002;89:2017–2023.
Harley RM. Mentha. In: Tutin TG, Heywood VH,
Burges NA, et al., eds, Flora Europaea,
Vol. 3. Cambridge: Cambridge University Press; 1972: 183–186.
Murray MJ, Lincoln DE. The genetic basis of acyclic
oil constituents in Mentha citrata Ehrh.
Genetics. 1970;65:457-471.
Tucker AO, Chambers HL. Mentha canadensis L. (Lamiaceae): a relict amphidiploid from the
Lower Tertiary. Taxon. 2002;51:703–718.
Wichtl M, ed. Herbal
Drugs and Phytopharmaceuticals, 3rd English ed. Stuttgart: medpharm
Scientific Publishers and Boca Raton, FL: CRC Press; 2004: 390–393.
Figure 47: a–b, Mentha ×piperita leaf and close-up of
lower surface; c, M. canadensis leaf
close-up.
|
|