FENNEL
Synonyms: Fennel fruit, Sweet
fennel, Wild fennel, Large fennel, Saunf (Hindi)
Biological
Source: Fennel consists
of the dried
ripe fruits of Foeniculum vulgare, belonging to
family Umbelliferae.
Macroscopy
:
The fruit is an entire cremocarps with pedicels,
oval-oblong and 5 to 10 mm long, 2 to 4 mm broad. It has greenish brown to
yellowish brown colour with five prominent primary ridges and a bifid stylopod
at the apex.
Microscopy
:
The transverse section of mericarp region of fennel
shows two prominent surfaces, the dorsal and the commissural surface. The
commisural surface has a carpophore and
two vittae, and
the dorsal surface
has a total
of five ridges.
The mericarp is divided
into pericarp, consisting
of the epicarp
and mesocarp; the
testa and the endocarp.
Epicarp consists of
polygonal cells of
epidermis which are
tangentially elongated and covered by
the cuticle. Mesocarp
has parenchyma cells
with five bicollateral vascular
bundles; below each
primary ridge a
lignified reticulate parenchyma
surrounds the vascular bundles. There are four vittae on dorsal surface and two
vittae on commisural or the ventral surface. Inner Epidermis or
Endocarp shows parquetry
arrangement (a group
of four to five cells
arranged parallelly at
acute angles with
groups of similar
cells in different direction). Testa is a
single-layered tangentially elongated cell with yellowish colour. Endosperm
consists of thick-walled, wide polyhedral, colourless cells. Cells contain
fixed oil, aleurone grains, and rosette crystals of calcium oxalate.
Microscopy
:
Fig. T. S. of Fennel
Fennel shows features of a typical umbelliferous
fruit.
Cremocarp
:
Cremocarp
is a variety
of schizocarp (splitting
fruit) which divides
into two one seeded portions, each corresponding to
one carpel. This carpel itself does not open to
liberate the seed;
thus, these schizocarps
are indehiscent fruits.
A cremocarp consists of two
parts, each of which is called a ‗mericarp‘. These two mericarps are
connected by a thick-walled sclerenchymatous central stalk
called ‗carpophore‘. A single seed is seen in each mericarp. Raphe is a single
ridge of vascular bundle at the middle of the commissural surface. The
carpophore is situated just in front of the raphe.
Transverse section
of a mericarp
shows two prominent
surfaces: commissural and dorsal.
The commissural surface is fl at with two distinct ridges and carpophores
in the
middle. The dorsal
surface shows three
ridges. Therefore, each
mericarp shows five primary ridges. A mericarp can be divided into
pericarp and seed.
a) Pericarp : It is made up
of epicarp, mesocarp and endocarp:
i.
Epicarp
:
The epicarp of the pericarp is also called
epidermis. It surrounds the entire fruit and consists of a layer of polygonal,
tabular, tangentially elongated cells with non striated and smooth cuticle and
shows occasional stomata.
ii.
Mesocarp
:
The bulk of
the mesocarp is
parenchymatous. It contains
much thickened and lignified
parenchyma in the
region of the
vascular strands of the ribs.
These thickened walls have
large, oval or
rounded pits; the
bands of thickening
between them give a
reticulate appearance to
the walls. This
is one of
the characteristic features of
the fennel fruit. Mesocarp shows five vascular bundles below each ridge
(thus ridges are
known as primary
ridges) and six
vittae. Reticulate lignified parenchyma is seen around the
vascular bundles.
Vascular bundles are five in number, bicollateral
and present below each ridge. Vittae are schizogenous oil cells, four vittae
present on the dorsal side and two on the commissural surface. Vittae
are about 250 μ maximum wide and taper towards the base
and up to
the apex of
the fruit. Walls
appear brown and
each duct is divided
into chambers by transverse
partitions. Vitta is
lined by an
epithelium of small polygonal
tabular cells. The
number and position
of vittae are
many times characteristic of
individual umbelliferous
fruits. Secondary ridges
occurred between the primary
ridges. The number,
distribution and arrangement
of ridges and
vittae give valuable information for identification of fruits.
iii.
Endocarp
:
It
consists of narrow
elongated cells having
a parquetry arrangement.
In the transverse section,
these cells appear
as long narrow
rectangular cells with scattered groups of very short cells.
Fig. Powder Microscopy of Fennel Fruit
|
Sr. No. |
Reagents |
Observations |
Characteristics |
|
1. |
Phlorogluinol+ conc. HCI(l:l) |
Red |
fibro-vascular fragments,
Reticulate Parenchyma |
|
2. |
Sudan red |
Red |
Vittae,
fixed oil, cuticle |
|
3. |
Alc. Picric acid |
Yellow |
Aleurone
grain |
Chemical
Constituents:
The best varieties of Fennel contain 4 to 5% of
volatile oil. The primary constituents of
volatile oil are
50 to 60%
of anethole, a
phenolic ester; and 18 to
22% of fenchone, a
ketone. Fenchone is
chemically a bicyclic
monoterpene which is a
colourless liquid and the odour and taste is pungent and camphoraceous. The oil
of Fennel has β-pinene, anisic acid,
phellandrine, and anisic
aldehyde. Fennel also contains about 20% fixed oil and 20%
proteins.
Uses:
Stomachic
Aromatic
Diuretic
Carminative
Diaphoretic
Digestive
Pectoral, and flavouring agent.
Anethole
may have estrogen-like
activity and inhibit spasms in smooth muscles. Fennel can increase
production of bile, used in the treatment
of infant colic,
to promote menstruation
in women, can
increase lactation, act as antipyretic, antimicrobial and
anti-inflammatory.
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