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Senna alexandrina Mill.
Standardized Common
Name: Senna
Other Common Names: Alexandrian Senna,
Indian Senna, Khartoum Senna, Nubia Senna, Tinnevelly Senna, True Senna
Family: Fabaceae
(Leguminosae)
Taxonomy: Senna
includes about 350 species, widely distributed in the tropics. The species now
included in Senna have previously been included in the closely related
genus Cassia, which now contains only about 30 species after the
exclusion of Senna. Senna remains a variable genus, including
trees, shrubs and herbs.
Senna alexandrina is native to
northern Africa and the Middle East. Its synonymy is complicated. Traditional
classifications recognized two or three separate species: S. angustifolia
(Vahl) Batka was the source of Tinnevelly senna and Bombay or East Indian
senna, whereas S. acutifolia (Del.) Batka and sometimes S.
alexandrina were said to be the source of Alexandrian senna. Recent
systematic treatments support the view that all of these plants belong to one
species. Among its most important synonyms are Cassia acutifolia Del., C.
alexandrina (Mill.) Thell., C. angustifolia Vahl, C. medicinalis
Bisch. C. senna L., S. acutifolia, and S. angustifolia.
Description: Perennial herb or
shrub. Stems erect to ascending, to 1.5 m high. Leaves alternate, stipulate,
pinnately compound, 5–20 cm long; stipules small, deciduous; leaflets
(3–)4–8(–10) pairs per leaf, lanceolate-elliptic, 1.5–5(–6) cm long,
0.4–1.0(–1.2) cm broad, pale olive to yellowish above or bluish; base cuneate
and slightly oblique; apex acute to mucronulate; venation pinnate.
Inflorescence racemose, to 3 cm long in flower elongating to 10–20 cm in fruit,
bracteate; bracts 5–7 mm long, obovate, deciduous; flowers almost sessile.
Hypanthium 2.5–4 mm long, resembling extension of pedicel; sepals 5, obovate,
reflexed; corolla bilaterally symmetrical, yellow to orange; petals 5,
(8–)13–15 mm long, conspicuously veined; fertile stamens 7, with 2 twice the
length of the other 5; staminodes 3; carpel single, longer than stamens,
pubescent. Fruit a legume, 3–5(–7) cm long, 1.5–2(–2.5) cm broad, oblong and
slightly curved, flattened, on short reflexed pedicel; apex and base rounded;
fruit wall papery, greenish brown to dark brown with paler striations and
sutures; seeds (5–)6–10, separated by membranes, 5–6 mm long, somewhat
pear-shaped, heart-shaped, or wedge-shaped, strongly flattened, light brown to
greenish or yellowish ivory.
Parts
in Commerce:
Leaflets or fruit
Identification:
Leaflets
- Lanceolate,
1.5–5 cm long and 0.4–1.2 cm broad
- Pale olive
green, sometimes yellowish above or bluish
- Apex acute,
sometimes mucronulate
- Base
asymmetrical, with one side tapering and one side slightly rounded
- Margins entire
- Slightly
leathery; brittle when dried
- Midrib
prominent, raised; secondary veins 3–5(–6) pairs, raised, curving toward
apex; tertiary veins netted, sometimes also raised
- Almost glabrous,
with only small, appressed hairs, found mostly around main veins
- Taste sweetish
and slightly bitter, mucilaginous
Fruit
- Oblong, slightly
curved or kidney-shaped and of same width along whole length; 3–5(–7) cm
long, 1.5–2.5 cm broad, and very flat
- Apex and base
rounded; base narrowing suddenly to tiny triangular extension at petiole
- Brownish green
to pale or dark brown or almost black, with fine irregular veins; veins
and sutures paler, yellowish
- Fruit wall
papery
- Seeds 5–6 mm
long, 3–4 mm broad, flattened, ovate to heart-shaped, pear-shaped or
wedge-shaped
- Seed apex broad,
with shallow notch; seed base narrowed, with areole forming a vertical
ridge
- Seeds pale brown
to greenish or yellowish ivory in color
- Seed surface
with tiny raised striations or bumps
- Taste somewhat
bitter, mucilaginous
Adulterants: Tinnevelly senna has
often been reported to be adulterated with S. italica Mill., also known
as S. obovata (Collad.) Link, which, despite its inclusion within C.
senna by Linnaeus, is not one of the commonly used medicinal species. The
leaves of S. auriculata (L.) Roxb. have also been reported. In the past,
admixture of the leaves of argel (Solenostemma argel (Del.) Hayne,
Asclepiadaceae) was a common practice. Other species appear in the literature
as occasional adulterants, including Coriaria myrtifolia L., Colutea
arborescens L. and Tephrosia apollinea Del. Characteristics that
could occur in misidentified leaflets or leaves include:
- Smaller than
expected, or longer and narrower, or broadly ovate or obovate in shape
- Bases
symmetrical
- Apices broad or
notched
- Leaf 3-veined,
or secondary veins indistinct or not pointing toward apex
- Most leaves
folding along midrib
- Long, erect or
dense hairs present on either leaf surface
- Silvery in color
Fruits are almost never confused, though the size
and shape of the pod and the size, shape, and ornamentation of the seeds should
be observed. The pods of S. italica are sharply curved almost into a
C-shape, whereas the pods of S. alexandrina are only gently curved.
References:
Irwin HS, Barneby RC. The American Cassiinae. A
synoptical revision of Leguminosae Tribe Cassieae subtribe Cassiinae in the New
World. Mem New York Bot Gard. 1982;35:1–918.
Luckow M. The cultivated species of Cassia, Senna,
and Chamaecrista (Leguminosae). Baileya. 1996;23:195–242.
Singh V. A note on the synonymy of Cassia senna
L. emend. Andrews. J Econ Tax Bot. 1987;9:467–469.
Wichtl M, ed. Herbal Drugs and
Phytopharmaceuticals, 3rd English
ed. Stuttgart: medpharm Scientific Publishers and Boca Raton, FL: CRC Press;
2004:563–571.
World Health
Organization. WHO Monographs on Selected Medicinal Plants. Vol. 1. Geneva: World Health Organization;
1999–2002:241–258.
Youngken HW. Text-Book of Pharmacognosy, 5th ed. Philadelphia, PA: The
Blakiston Company; 1943:460–467.
Figure 66: a–c, Senna alexandrina leaf, leaf close-up and fruit; d–f, S.
italica leaf, leaf close-up and fruit.
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