Tea: Biological source, Chemical Constituents, Morphological features, Uses and MCQs
TEA
1. Biological source:
• The botanical name of tea is Camellia sinensis.
• The biological source of tea is prepared leaves and leaf buds of it.
• It belongs to the theaceae family.
• Commonly it is known as tea plant or tea shrub.
2. Morphological features:
• Tea is a evergreen shrub or small tree.
• It is usually trimmed to below 2 m during the cultivation of its leaves.
• It is consist of strong taproot.
• The color of flowers are yellow – white.
• The size of flower is 2.5-4 cm in diameter.
• Its flowers consist of 7 or 8 petals.
• The size of leaves are 4-15 cm long and 2-5 cm broad.
• The young , light green leaves have short and white hairs on the underside.
• Older leaves are deep green in color.
• The tea plant is polymorphic species.
• Its strong taproot giving rise to a surface mat of feeder roots with endotrophic mycorrhizae.
• Leaves are alternate and lanceolate to obovate.
• Leaves are pubescent and sometimes become the glabrous, serrate, acute or acuminate.
• Flowers are having 1-3 in number.
• Flowers are in axillary or subterminal cymes.
• Flowers are aromatic and consist of 5-7 sepal and petals.
• The pedicles are about 5-15 mm long.
• Ovary 3-5 carpellate and each carple have 4-6 ovulate.
• Capsules are depressed- globose, brownish, lobate and 2 cm broad.
• Capsules are having 1-3 sub- globose seeds in each lobe.
3. Chemical constituents:
• The leaves of tea consist of thease which is an enzymatic mixture containing an oxidase, which partly converts the phlobatannin into phlobaphene, as chemical constituent.
• Other chemical constituent present in tea leaves are tannins, caffeine.
• It contain 1-5% of tannin and 10-24% of caffeine.
• In tea leaves theobromine is also present in small amount.
• Tea leaves also consist of theophylline and volatile oil.
• Alkaloid content also present in tea leaves but its amount only depend on season and age of tea leaves.
• Seeds of C. sinensis contain acylated oleane type triterpenes having antiallergic activities.
• Major chemical constituents are catechins and theoflavins.
• Physically, tea has both qualities of solution and suspension.
• Caffeine is about 3% of tea’s dry weight.
• Black tea contain dietary mineral manganese about 0.5 miligrams.
• Fluoride is also present in tea in small amount.
• Polyphenols are most abundant chemical constituents present in tea.(30-40%)
• Example of polyphenols present in tea leaves are flavonoids , epigallocatechin gallate and other catechins.
4. Uses:
• Drinking black or green tea have beneficial effects on body.
• It is non-alcoholic beverages.
• It has strong antioxidant property due to presence of caffeine in addition with polyphenols.
• It also have free radical scavenging properties.
• It helps in the inhibition of angiogenesis i.e. the process involving the growth of blood vessel essential for tumour growth and metastasis.
• It is used to treat genetic haemochromatosis via inhibition of absorption of iron by tannates and other ligands.
• It helps to treat blindness caused due to diabetes which is an angiogenic condition.
• It helps to lower the risk of ischemic heart disease in older man.
• The major application of tea is to maintain cardiovascular health.
• It helps in the prevention of cancer.
• Green and black tea helps to protect against obesity .
• It also helps to treat alzheimer’s disease.
5. Adulterants:
The common adulterants of soapstone, gypsum, graphite, indigo dye and Prussian blue dye substances.
6. MULTIPLE CHOICE QUESTIONS:
1. What is the botanical name of tea?
(a) Allium cepa
(b) Camellia sinensis
(c) Sedum acre
(d) Lupinus texensis
2. What is the major biological source of tea?
(a) Leaves
(b) Root
(c) Bark
(d) Flowers
3. Tea belongs to which plant family?
(a) Acanthaceae
(b) Amaryllidaceae
(c) Theaceae
(d) Apiaceae
4. Match the flowing with respect to the chemical composition of plants.
I. Opium A. Ephedrine
II. Ipecac B. Albumin
III. Ephedra C. Emetine
IV. Tea D. Catechins
(a) I-A,II-B,III-C,IV-D
(b) I-B,II-C,III-A,IV-D
(c) I-C,II-D,III-B,IV-A
(d) I-D,II-A,III-B,IV-C
5. Choose the incorrect statement with respect to the medicinal uses of plants.
I. Opium is used to treat constipation.
II. Tea is used to treat mysthenia gravis disease.
III. Ipecac is used to treat amoebic dysentery.
IV. Nux vomica used to increase the flow of gastric juice.
(a) Only II
(b) Both III and IV
(c) Only III
(d) Both I and IV
6. Flowers of tea shrub are
(a) 1-3 in number.
(b) It consist of 7 or 8 petals
(c) Lanceolate to obovate in shape
(d) Both a and b
7. Leaves of tea shrub are
(a) Alternate in arrangement
(b) Young leaves are light green in color and old leaves are dark green in color
(c) They are pubescent
(d) All of the above
8. Which dye from the following work as an adulterant of tea shrub?
(a) Indigo dye
(b) Alacian blue
(c) Chrysoidine R
(d) Congo red
9. What are the most common adulterant of tea?
(a ) Gypsum
(b) Soapstone
(c) graphite
(d) All of the above
10. Tea is used to treat
(a) Diabetes
(b) Obesity
(c) Alzheimer’s disease
(d) All of the above
ANSWERS:
1. (b)
2. (a)
3. (c)
4. (b)
5. (a)
6. (d)
7. (d)
8. (a)
9. (d)
10. (d)
REFERENCE:
Evans W.C, Editors. Trease and Evans Pharmacognosy. New York, Saunders Elsevier; 2009, p. 410,460.