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Rauwolfia serpentina is a plant whose root had been used in Indian medicine for centuries. In the 20th century chemists set out to find which molecules in the root actually did something. One of the first to publish a detailed chemical study was Salimuzzaman Siddiqui. This post covers what can be verified about him, what his 1931 paper was, how the story of the root continued, and a short calculation with one of the compounds linked to his name.
Who was Salimuzzaman Siddiqui?
His Royal Society biographical memoir, written by Muhammad Akhtar, gives his dates as 19 October 1897 to 14 April 1994 and calls him a true Renaissance man. His early university education was in philosophy. He wrote poetry, loved Urdu and Persian verse, and was a serious painter of modern art. Above all, the memoir says, he was a natural product chemist of the highest quality, with a gift for isolating pharmacologically active compounds from plants of the Indian subcontinent. When others later worked out the structures of those compounds, they turned out to contain new architectural features.
That division of labour is worth noticing. Isolating a pure compound from a root and proving its structure were separate achievements, often by different people.
What was the 1931 paper?
The paper was "Chemical Examination of the Roots of Rauwolfia Serpentina, Benth.", by Salimuzzaman Siddiqui and Rafat Hussain Siddiqui, dated 1931. A scanned copy, covering pages 667 to 680, is kept in the Zenodo repository. Salimuzzaman Siddiqui followed it with a further note on the alkaloids of the same plant in 1939.
Alkaloids are nitrogen-containing compounds made by plants, and most behave as bases. One of the Rauwolfia alkaloids, ajmaline, is so closely tied to him that the pharmacologist Raymond-Hamet published papers in the Comptes rendus of the French Academy of Sciences in 1957 and 1965 on the physiological properties of "pure Siddiqui ajmaline".
What happened to Rauwolfia after Siddiqui?
The plant became internationally famous through medicine. The cardiologist R. J. Vakil, in a 1955 review in Circulation, wrote that the root had been in use in India for hundreds of years for many unrelated ailments, and that after his 1949 English-language report on fifty cases of essential hypertension the plant gained worldwide attention for high blood pressure. That report was his clinical trial in the British Heart Journal.
The compound responsible for the sedative effect was isolated later. In 1952 Müller, Schlittler and Bein reported reserpine as the sedative principle of Rauwolfia serpentina in Experientia. The Rauwolfia story therefore runs through several people: Siddiqui's early chemistry, Vakil's clinical trials and the Swiss team's reserpine. This post is history, not medical advice; Rauwolfia compounds are powerful drugs and should only be used under a doctor's care.
Worked example: checking a formula
PubChem lists ajmaline as C20H26N2O2 with a molar mass of 326.4 g/mol. You can check that from atomic masses:
C: 20 × 12.011 = 240.22
H: 26 × 1.008 = 26.21
N: 2 × 14.007 = 28.01
O: 2 × 15.999 = 32.00
Total: 240.22 + 26.21 + 28.01 + 32.00 = 326.44 g/mol
Now the percentage of nitrogen: 28.01 ÷ 326.44 × 100 = 8.58 per cent.
Compare reserpine, which PubChem lists as C33H40N2O9, 608.7 g/mol. It also has two nitrogen atoms, so its nitrogen share is 28.01 ÷ 608.7 × 100 = 4.60 per cent. Two alkaloids from the same root can be told apart by numbers like these. Measuring the percentage of each element and comparing it with a proposed formula is the kind of check elemental analysis provides, and you practise the same calculation in Class 11 when you find empirical formulas.
Common mistakes:
Rounding atomic masses too early. Using C = 12 and H = 1 gives 326 exactly and hides small differences between candidate formulas.
Forgetting to multiply by the number of atoms. N2 means 2 × 14.007, not 14.007.
Confusing the plant with the compound. "Rauwolfia" is a root containing many alkaloids; ajmaline and reserpine are single, different molecules.
What can a student take from Siddiqui?
The memoir's picture is of a chemist who was also a painter, a poet and a reader of philosophy, and whose experimental skill showed in getting difficult compounds pure. Two habits carry over to your own work. First, separate what you have measured from what you have inferred. Second, check a formula against numbers before trusting it. If you want to see how chemists separate mixtures, our post on purification and chromatography covers the methods in the syllabus.
If percentage composition or empirical formulas still trip you up, the Fermi Problem Library has a step-by-step solver that explains the reasoning rather than printing an answer.
Try it now: work out the percentage of oxygen in reserpine from its formula, and check that the percentages of all four elements add up to 100.
