Quinine is a common drug for malaria that is obtained from a plant. Which part of the plant yields this drug ?

Question

UnlockIAS · Accepted Answer

Correct — A, Stem bark. Quinine is an alkaloid of the cinchona tree, a genus of the family Rubiaceae native to the tropical Andean forests of western South America, and the part of the tree that is harvested, dried, powdered and extracted is the bark of the trunk and branches — the material the old trade called Peruvian bark or Jesuit's bark. The pharmacopoeial drug is literally 'cinchona bark': strips are peeled from the standing trunk or from felled stems, dried, and worked up for their alkaloid content. Two French chemists, Pierre Joseph Pelletier and Joseph Bienaimé Caventou, first isolated pure quinine from that bark in 1820, and the same bark yields three more alkaloids of the same family — quinidine, cinchonine and cinchonidine — which is why the whole class is called the cinchona alkaloids. Cinchona remains the only economically practical source of quinine; two centuries of chemistry have not produced a synthesis that can compete with a tree, and the commercially decisive species, Cinchona ledgeriana, carries roughly 8 to 13 per cent quinine in its bark. The species matters less than the tissue: what the bark carries in double-digit percentages, the leaves do not, which is exactly what the question is testing. Since option (a) is right, option (d) 'None of the above' cannot be. Note the wording the Commission chose — 'stem bark' rather than a bare 'bark' — and it is the precise term, because bark in the botanical sense is everything outside the vascular cambium and it can be taken from stem or root; the drug of commerce comes from the stem.

Why the other options are wrong — (b) Leaves are the default guess for any plant-derived substance, because that is where photosynthesis happens and where the familiar plant drugs of everyday life — tea, tobacco, mint — come from. Cinchona leaves are not the drug source; the alkaloid is concentrated in the bark, and no pharmacopoeia lists a leaf preparation of cinchona.  (c) The near-miss, and worth understanding rather than merely rejecting. Cinchona root bark does contain alkaloids and was traded in small quantities in the nineteenth century, but the root as such is not the source, and the medicinal material of commerce and of the pharmacopoeias is the bark of the stem and branches. An option that says 'Root' — not 'root bark' — names the wrong organ and the wrong tissue at once.  (d) This escape option is only correct when all three named choices fail, and here the first one succeeds outright: cinchona stem bark is the source of quinine. Reach for a 'None of the above' only after you can say specifically why each of the other three is false — on this question you cannot, because (a) is true.

Concept: Plant-derived drugs are classified by the organ they are extracted from, and examiners test exactly that pairing. Quinine belongs to the alkaloids — nitrogen-containing, bitter, physiologically potent plant compounds, the group that also contains morphine, nicotine, caffeine and reserpine. In cinchona the alkaloids accumulate in the bark, the tissue outside the vascular cambium, which is why the tree is stripped rather than uprooted or defoliated. Cinchona species are shrubs or small trees five to fifteen metres tall with opposite leaves and white, pink or red flowers in terminal panicles; Europeans called them fever trees for what the bark did. The bark was in use against fevers in the Andes before European contact, reached Europe with Jesuit missionaries in the 1630s, and entered the London Pharmacopoeia as Cortex Peruanus in 1677. It is the first case in history of a chemical compound being used to treat an infectious disease.

State PCS 2025 Q101 — Science & Technology PYQ with Answer

State PCS 2025 Q101 — Science & Technology PYQ with Answer