Pharmacognostical Studies on Leaf of Tribulus terrestris L.

Mamdouh N. Samy¹*, Mokhtar M. Bishr², Ahmed A. Ahmed³, Hanaa M. Sayed⁴ and Mohamed S. Kamel¹

¹Department of Pharmacognosy, Faculty of Pharmacy, Minia University, Minia 61519, Egypt.

²Research and Development Department, Mepaco Company, Cairo, 11361, Egypt.

³Department of Organic Chemistry, Faculty of Science, Minia University, Minia 61519, Egypt.

⁴Department of Pharmacognosy, Faculty of Pharmacy, Assuit University, Assuit 71526, Egypt.

ABSTRACT:

Tribulus terrestris L. (family Zygophyllaceae) is a prostrate branched herb. The stems have monopodial branching and carry opposite compound paripinnate leaves and yellow simple flowers. The fruit is schizocarpic. The present paper deals with comprehensive pharmacognostical studies on leaf part of this plant, including macroscopical and microscopical studies and preliminary examination of leaf powder. This will help in the identification of powder drug prior using in any herbal formulations.

KEYWORDS: Tribulus terrestris, Zygophyllaceae, pharmacognostical study, leaf.

INTRODUCTION:

The genus Tribulus belongs to family Zygophyllaceae comprises approximately 25 species which grow as prostrate hairy herbs in tropical and warm regions^1,2. Tribulus terrestris L. (Zygophyllaceae) (Fig. 1) is commonly known as devil's thorn, cat head, puncture vine, goat head and caltrop³. It is a herbaceous, annual, prostrate or semierect, diffusely branched herb ⁴;native in dry and sandy districts in South Europe to Central Asia and in tropical and South Africa⁵, growing in India, other warm countries such as Ceylon⁶, desert plains, waste ground, weed of cultivation and Mediterranean region¹. It is used in folk medicine to increase spermatogenesis, for treatment of eye troubles, edema, abdominal distension, leucorrhea and impotence, as aphrodisiac, galactagogue, anti-inflammatory, antidiarrheal and diuretic ⁴.

MATERIALS AND METHODS:

Plant material:

The leaves of T. terrestris were collected during the flowering and fruiting stage in October 2004 from the green areas of Minia University Campus, Minia, Egypt. A voucher specimen of the plant is deposited in the Herbarium of Faculty of Pharmacy, Minia University, Egypt (Minia-04-Mar-TT).

Macroscopical study:

The leaves (Fig. 2 and 3) are opposite compound paripinnate of alternate unequal pairs (one of each pair usually smaller than the other). The leaflets are usually arranged on the rachis in 5-6 pairs measuring 0.2 × 0.4 to 0.5 × 1.2 cm. They are sessile with asymmetric base, more dark green on upper surface and paler on the lower.

The leaflet has an entire margin, oblong to linear-oblong lamina and acute apex. The midrib divides leaflet into two unequal halves 0.1 to 0.2 and 0.2 to 0.3 cm. Stipules are present, 3-4 mm, lanceolate and hairy.

Fig. 1: photo of Tribulus terrestris

Fig. 2: photos of the leaf

Fig. 3: sketch of the leaf

Microscopical study:

A-The leaflet:

The lamina:

A transverse section through the lamina in the mid rib region (Fig. 4, 5, 6 and 7) shows a prominent midrib on the lower surface. It shows an isobilateral structure with upper palisade and lower palisade enclosing in between spongy mesophyll. The upper palisade consisting of one row of continuous columnar cells while the lower palisade is interrupted in the mid rib region by parenchyma cells and is separated from the lower epidermis by one layer of colourless water-storage cells ⁷. The vascular system of the mid rib is formed of collateral vascular bundle enveloped by sheath of comparatively enlarged cortical parenchymatous cells with thin walls and free from contents. Both the upper and lower epidermis carries stiff hairs and nonglandular unicellular hairs.

The epidermis:

The upper epidermis:

The upper epidermis is formed of one row of usually square to subrectangular cells as seen in transverse section. In surface view (Fig. 11 and 12) the epidermal cells are polygonal usually elongated, occasionally isodiametric with straight anticlinal walls, being about 30 to 70 µ in width, 30 to 70 µ in length and 15 to 25 µ in height. They are covered with thick smooth cuticle. Numerous stomata are present, being of anomocytic type which is oval to rounded, surrounded with 4-5 cells and measuring 20 to 25 µ in diameter and 25 to 30 µ in length. Non-glandular, unicellular hairs are present with thick walls and narrow lumen, measuring from 20 to 40 µ in width and 180 to 900 µ in length.

The lower epidermis:

The lower epidermis is formed of one row of usually square to subrectangular cells as seen in transverse section. In surface view (Fig. 5 and 6) the epidermal cells are polygonal usually elongated, occasionally isodiametric with straight anticlinal walls, being about 20 to 40 µ in width, 40 to 70 µ in length and 10 to 25 µ in height. They are covered with smooth cuticle. Numerous stomata are present, being of anomocytic type which is oval to rounded, surrounded with 4-5 cells and measuring 20 to 25 µ in diameter and 20 to 30 µ in length. Non-glandular, unicellular hairs are present with thick walls and narrow lumen.

The mesophyll:

The mesophyll is isobilateral showing upper palisade beneath the upper epidermis forming a continuous layer and measuring 10 to 20 µ in width and 60 to 80 µ in length, while the lower palisade is separated from the lower epidermis by one layer of colourless water-storage cells interrupting by the cortical tissue in midrib region and big vein and measuring 10 to 20 µ in width and 25 to 40 µ in length. The palisade is formed of one row of cylindrical, columnar, thin-walled cells with very narrow intercellular spaces and containing chloroplast. The spongy tissue consists of thin-walled, rounded parenchymatous cells with fairly wide intercellular spaces containing scattered cluster crystals of calcium oxalate measuring 25 to 30 µ in diameter. The mesophyll is traversed by separated strands of small vascular bundles representing the lateral veins.

The cortical tissue:

The cortical tissue consists of ordinary parenchyma surrounding the main vascular bundle of the midrib. It widens below the bundle and consists of 3 to 4 rows of parenchyma containing scattered cluster crystals of calcium oxalate measuring 25 to 30 µ in diameter.

The vascular tissue:

The vascular tissue is represented by the main vascular bundle of the mid rib and the lateral bundles of the veins. Each vascular bundle is formed of upper xylem region and lower phloem region and more or less surrounded by parenchymatous pericycle.

The pericycle:

The pericycle is formed of two arcs of parenchymatous cells surrounding the vascular bundle. The lower arc of the pericycle abutting surrounding the phloem from below and consists of 3 rows, while the upper arc is smaller.

The xylem:

The xylem is formed of radial rows of lignified spirally thickened vessels and non lignified wood parenchyma.

The phloem:

It is formed of a complete narrow zone of shining, thin-walled, soft, cellulosic elements.

Fig. 4: A Photo of T.S. of the mid rib × 162.5

Fig. 5: A Photo of T.S. of the lamina × 162.5

Fig. 6: Sketch of T.S. of the mid rib × 250

Fig. 7: Sketch of T.S. of the lamina × 250

B-The rachis:

A transverse section in the rachis (Fig. 8, 9 and 10) is subrounded or somewhat circular in shape with a groove on the upper surface. Within the epidermis is the ground tissue representing the whole internal structure and is formed of ordinary parenchyma containing scattered cluster crystals of calcium oxalate. The ground tissue is traversed by about four main separated vascular bundles. The upper two notches enclose two rows of palisade cells and one collateral vascular bundle in each notch; the vascular elements are arranged horizontally. There are groups of few layered pericyclic fibers varying from cellulosic thickening to slightly lignified abutting the phloem of each bundle. The phloem is very narrow, the xylem is radiating, comparatively wide and with the primary xylem projecting out into the medulla of the rachis.

The epidermis:

The epidermis is formed of one row of usually square to subrectangular cells as seen in transverse section. In surface view (Fig. 11 and 12) the epidermal cells are polygonal usually elongated, occasionally isodiametric with straight anticlinal walls; the walls varies from beaded walls to sometimes thin walls of the epidermal cells around the stoma, being about 10 to 30 µ in width, 40 to 60 µ in length and 15 to 20 µ in heigth. They are covered with smooth thick cuticle. Occasional stomata are present, being of anomocytic type, surrounded with 4-5 cells and measuring 20 to 25 µ in diameter and 25 to 30 µ in length. Stiff-like hairs with slightly lignified walls and wide lumen and long non-glandular, unicellular hairs with rounded base and acute apices are present being about 30 to 40 µ in width and 500 to 520 µ in length.

The palisade:

The palisade under the notch is formed of two rows of cylindrical, columnar, thin-walled cells with very narrow intercellular spaces and containing chloroplast and measuring 10 to 20 µ in width and 20 to 50 µ in length.

The ground tissue:

The ground tissue is formed of many rows of ordinary, thin-walled parenchyma with numerous, fairly wide intercellular spaces. Scattered cluster crystals of calcium oxalate measuring from 50 to 60 µ in diameter are present in the parenchyma.

The pericycle:

The pericycle is formed of fibers varying from cellulosic thickening to slightly lignified, above the vascular elements. The fiber has an acute end and slightly wide lumen, measuring 550 to 800 µ in length and about 10 to 30 µ in width.

Fig. 8: A photo of T.S. of the rachis × 100

Fig. 9: Photos of T.S. of the rachis × 200

The phloem:

It is formed of narrow patch of phloem abutting the xylem and consisting of shining, thin-walled, soft, cellulosic elements.

The xylem:

The xylem is formed of radial rows of lignified spirally thickened vessels and non lignified wood parenchyma.

Fig. 10: Sketch of T.S. of the rachis × 200

The powder of the leaf:

The powder of the leaf [Fig. 11 and 12] is green in color with faint characteristic odor and bitter taste. The main diagnostic microscopic elements are:

1- Fragments of upper and lower epidermal cells of the lamina consisting of polygonal usually elongated, occasionally isodiametric with straight anticlinal walls covered with smooth cuticle, showing anomocytic stomata.

2- Nonglandular, unicellular hairs with thick walls and narrow lumen.

3- Fragment of lignified xylem vessels with spiral thickening.

4- Fragment of palisade.

5- Scattered cluster crystals of calcium oxalate.

6- Fragment of epidermal cells of the rachis consisting of polygonal usually elongated, occasionally isodiametric with anticlinal walls varies from beaded to straight walls, covered with smooth cuticle, showing anomocytic stomata.

7- Nonglandular, unicellular hairs with thick walls and narrow lumen from the rachis.

8- Fragment of lignified xylem vessels with spiral thickening from the rachis.

9- Lignified pericyclic fiber from the rachis.