History of Alkaloids

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Questions and Answers

What is the primary use of alkaloidal precipitating agents?

To enhance plant growth

To create color changes in plants

To indicate the absence or presence of alkaloids (correct)

To produce medicinal outcomes

Which of the following is NOT a disadvantage of using precipitating agents for alkaloids?

They require complex procedures

They may produce misleading results

They can be water soluble (correct)

They may interfere with non-alkaloids

Which reagent is classified as a halogen-containing precipitating agent?

Dragendorff’s Reagent

Hager's Reagent

Wagner’s Reagent (correct)

Mayer’s Reagent

What type of chemical compound does Hager's Reagent represent?

An organic acid Signup and view all the answers

Which method employs alkalis for the extraction of alkaloids?

Method I Signup and view all the answers

In which of the following methods are alkaloids extracted with water immiscible organic solvents?

Method I Signup and view all the answers

Which of the following reagents is NOT a qualitative test for alkaloids?

Tannic Acid Signup and view all the answers

Which reagent is formed by combining formaldehyde and concentrated sulfuric acid?

Marqui's Reagent Signup and view all the answers

Which amino acid is NOT typically a precursor for alkaloids?

Glutamine Signup and view all the answers

What is the primary purpose of acidifying an extract during the purification of crude alkaloidal fractions?

To convert alkaloids into salts Signup and view all the answers

Which method is NOT typically used for the identification of alkaloids?

Spectrophotometry Signup and view all the answers

What structural feature is common among alkaloids?

Presence of a nitrogen atom Signup and view all the answers

Which alkaloid structure is associated with tropane?

Piperidine Signup and view all the answers

What is the outcome of repeated acid-base procedures in alkaloid extraction?

Formation of crystalline salts Signup and view all the answers

Which of the following is a characteristic property determined during the identification of alkaloids?

Melting point Signup and view all the answers

The precursor amino acid tryptophan is primarily associated with which alkaloidal structure?

Indole Signup and view all the answers

Who coined the term 'alkaloid'?

Meissner Signup and view all the answers

Which alkaloid was isolated first in the early 19th century?

Morphine Signup and view all the answers

In which part of the plant is coniine typically found?

Roots Signup and view all the answers

Which family is known to be rich in alkaloids?

Rubiaceae Signup and view all the answers

What is one of the functions of alkaloids in plants?

Serving as protective agents against herbivores Signup and view all the answers

Which alkaloid was discovered last among those listed in the early 19th century?

Cocaine Signup and view all the answers

What role do alkaloids serve in cases of nitrogen deficiency?

They source nitrogen Signup and view all the answers

Which of the following families is free from alkaloids?

Rosaceae Signup and view all the answers

Study Notes

Brief History of Alkaloids

The term alkaloid was introduced by A. Meissner in 1819.
Alkaloids serve various roles such as poisons, medicines, and stimulants.
French chemists Derosne (1803) isolated narcotine, while Sertürner isolated morphine (1806, 1816).
Key discoveries in early alkaloid chemistry include quinine (1820) and strychnine (1818) by Pelletier and Caventou.
Caffeine was identified in 1820, along with other alkaloids like nicotine (1828) and cocaine (1860).
Coniine was the first alkaloid to have its structure established (1870) and synthesized (1889).

Occurrence in Plants

Alkaloids are rare in lower plants and are more abundant in dicots than in monocots.
Rich sources of alkaloids include the families: Apocynaceae, Rubiaceae, Solanaceae, and Papaveraceae.
Families typically lacking alkaloids include Rosaceae and Labiatae.

Distribution of Alkaloids

Present in various plant parts, including:
- All parts: Example - Datura
- Barks: Example - Cinchona
- Seeds: Example - Nux vomica
- Roots: Example - Aconite
- Fruits: Example - Black pepper
- Leaves: Example - Tobacco
- Latex: Example - Opium

Function in Plants

Alkaloids serve as protective agents against herbivores due to their bitter taste and toxicity.
They can signify the end products of detoxification or function as a nitrogen source.
Act as growth regulators and energy sources under nutrient deficiencies.
Typically water-insoluble and can create precipitates to indicate alkaloid presence in tests.

Alkaloidal Precipitating Agents

Double salt reagents include:
- Mayer’s Reagent: Potassium Mercuric Iodide.
- Dragendorff’s Reagent: Potassium Iodobismethate.
Halogen-containing reagents:
- Wagner’s Reagent: Iodine/Potassium Iodide.
Organic acids such as:
- Hager’s Reagent: Picric Acid and Tannic Acid.
Oxygenated high molecular weight acids include phosphomolybdic and phosphotungestic acids.

Qualitative Tests for Alkaloids

Common color reagents include:
- Froehd’s Reagent: Phosphomolybdic acid.
- Marqui’s Reagent: Formaldehyde with concentrated sulfuric acid.
- Erdmann’s Reagent: Concentrated nitric and sulfuric acids.

Extraction and Isolation of Alkaloids

Extraction methods:
- Method I: Use of alkalis with water-immiscible solvents.
- Method II: Extraction using dilute acid in aqueous alcohol.
- Method III: Water-soluble organic solvents like methanol or ethanol.
Repeated acid-base procedures help purify alkaloids by selectively dissolving impurities using organic solvents.

Identification Techniques for Alkaloids

Melting point determination and color tests assist in identifying alkaloids.
Advanced methods include HPLC, GC, GC-MS, UV, IR, NMR, and MS.

Alkaloid Biosynthesis

Alkaloids are synthesized from amino acids and other plant amines.
Key amino acids involved in alkaloid formation include phenylalanine, tyrosine, tryptophan, histidine, lysine, and ornithine.
Other biochemical precursors, such as terpenes or steroids, may contribute to the alkaloidal skeleton.

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Description

Explore the fascinating history of alkaloids, from their introduction by A. Meissner in 1819 to significant discoveries by French chemists like Derosne and Sertürner. This quiz covers the roles, isolation, and identification of important alkaloids such as morphine, quinine, and caffeine.