Natural Product Chemistry Chapter 3

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Questions and Answers

Why is authentication of plant material necessary?

To establish the identity of the plant species (correct)
To preserve the active constituents of the plant material
To ease the transportation of plant material
To ensure the plant material is not affected by viral, bacterial, or fungal infection

What is the purpose of drying plant materials?

To enhance the colour of the plant material
To inhibit the growth of microorganisms and preserve active constituents (correct)
To ease the grinding of the plant material
To change the shape and appearance of the plant material

What is the advantage of homogenizing fresh leaves by dropping them into boiling solvent?

To change the colour of the leaves
To preserve the shape and appearance of the leaves
To enhance the odour of the leaves
To stabilize the leaves and facilitate extraction (correct)

What is the consequence of large biomass particles during extraction?

They are poorly extracted (B) Signup and view all the answers

Why is grinding of dried plant materials necessary?

To ensure effective extraction of phytochemicals (C) Signup and view all the answers

What is the purpose of garbling of dried plants?

To sort and remove impurities from the plant material (C) Signup and view all the answers

What is the advantage of using a course mill followed by a fine mill during grinding?

To produce a fine powder with a higher surface area (D) Signup and view all the answers

What is the implication of changes in size, weight, shape, and appearance during drying?

The plant material undergoes physical transformations (C) Signup and view all the answers

What is the common name of the plant with the scientific name Elaies guineensis?

Oil palm (D) Signup and view all the answers

What type of phytochemical is citral?

Monoterpenoid (C) Signup and view all the answers

What is the purpose of grinding in phytochemical screening?

To increase the surface area of the plant sample (D) Signup and view all the answers

What is the type of phytochemical responsible for red, orange, or purple colors?

Anthocyanidin (B) Signup and view all the answers

What is the purpose of qualitative analysis of phytochemicals?

To identify the type of phytochemicals present (C) Signup and view all the answers

What is the type of spectroscopy used to determine the structure of unknown compounds?

All of the above (D) Signup and view all the answers

What is the purpose of toxicity evaluation in phytochemical screening?

To determine the safety of phytochemicals for human use (B) Signup and view all the answers

What is the first step in phytochemical screening?

Selection of promising plant materials (C) Signup and view all the answers

What is the purpose of chromatographic methods in phytochemical screening?

To separate and purify phytochemicals (A) Signup and view all the answers

What is the type of phytochemical present in carrot and pumpkin?

Carotenoid (C) Signup and view all the answers

What is the main advantage of the cold extraction method?

It is a soft extraction method that does not heat the extract, reducing the potential degradation of natural products (B) Signup and view all the answers

What is the purpose of acidification in the extraction of organic compounds?

To increase the solubility of aromatic acids and phenols (B) Signup and view all the answers

What is the order of solvents used in cold extraction?

Hexane, ethyl acetate, methanol, water (C) Signup and view all the answers

What is the main difference between cold extraction and hot percolation?

The temperature at which the extraction is performed (B) Signup and view all the answers

What is the purpose of using sequential solvents of increasing polarity in cold extraction?

To divide natural products according to their solubility and polarity (B) Signup and view all the answers

What is the typical solvent used in hot percolation?

Ethanol or aqueous ethanol mixtures (D) Signup and view all the answers

What is a common problem that can occur when using alcohol as a solvent?

The extraction of pigments and resins (B) Signup and view all the answers

What is the purpose of basification in the extraction of organic compounds?

To enable the use of water-immiscible solvents for the extraction of alkaloids (A) Signup and view all the answers

What is the advantage of using ethanol in extraction?

It extracts the majority of lipophilic and polar compounds (A) Signup and view all the answers

Why is it necessary to perform a pilot experiment before attempting hot percolation?

To assess if the extraction method degrades bioactive natural products (B) Signup and view all the answers

What is the purpose of decoction?

To extract active ingredients that don't modify with temperature (B) Signup and view all the answers

What is a limitation of Soxhlet extraction?

It can cause degradation of labile compounds (C) Signup and view all the answers

What is the principle of supercritical fluid extraction?

It uses the solvating properties of gases under pressure (C) Signup and view all the answers

What is the advantage of Soxhlet extraction?

It is the best extraction method for the recovery of big yields of extract (B) Signup and view all the answers

What is a characteristic of Soxhlet extraction?

It uses a reflux condenser (C) Signup and view all the answers

What is a limitation of total extraction?

It is not suitable for all types of compounds (B) Signup and view all the answers

What is the purpose of Molisch's Test?

Detection of reducing sugars (A) Signup and view all the answers

Which of the following methods is used for total alkaloid determination?

Harbone.J.(1973) (A) Signup and view all the answers

What is the method used for total saponins determination?

Obdoni B, Ochuko P.(2001) (D) Signup and view all the answers

What is the purpose of Task 7 in phytochemical analysis?

To observe and record the characteristics of a plant sample (A) Signup and view all the answers

Which of the following is NOT a step in phytochemical analysis?

Cultivating plant samples (A) Signup and view all the answers

What is the purpose of the methods mentioned in the content?

To determine the quantity of phytochemicals present (A) Signup and view all the answers

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Study Notes

Extraction, Identification, and Characterization of Bioactive Molecules from Natural Sources

Screening of Phytochemicals
- Types of phytochemicals: carotenoids (e.g. β-Carotene), terpenoids (e.g. Citral), flavonoids (e.g. Naringenin), anthocyanin/anthocyanidin
- Collection of plant samples: fresh and dried, with authentication by taxonomy expert, field botanist, or voucher specimen
- Drying of plant materials: natural drying (shade and sunlight) or artificial drying (hot air or freeze-drying), to inhibit microbial growth and preserve active constituents
- Grinding of dried plants: to increase surface area for efficient extraction
- Garbling of dried plants: using solvents like water, light petroleum, ether, and chloroform, depending on the target phytochemicals

Methods of Extraction of Phytochemicals

Cold Extraction
- Simple and soft extraction method
- Uses sequential solvents of increasing polarity (e.g. hexane, ethyl acetate, methanol, water)
- Enables division of natural products according to solubility and polarity
Hot Percolation
- Uses solvents like ethanol or aqueous ethanol mixtures
- Heating may degrade labile compounds, so pilot experiment is necessary
- Also known as total extraction
Decoction
- Used for active ingredients that don't modify with temperature
- Boiling in water for 15-60 minutes
Soxhlet Extraction
- Efficient method for high-yield extraction
- Continuous refluxing of solvent through biomass
- Suitable for drug lead discovery
Supercritical Fluid Extraction
- Uses gases under pressure with solvating properties
- Example: Molisch's Test for detecting reducing sugars

Analysis and Detection of Phytochemicals

Qualitative Analysis
- Detection of reducing sugars, saponins, phytosterols, phenolic compounds, tannins, flavonoids, proteins, and amino acids
Quantitative Analysis
- Total phenols determination: Hagerman et al. (2000)
- Total alkaloid determination: Harbone (1973)
- Total flavonoids determination: Kumaran et al. (2006)
- Total tannins determination: Van-Burden & Robinson (1981)
- Total saponins determination: Obdoni et al. (2001)

Task 7: Individual Activity

Observe a plant sample, search for related articles, and report on:
- Phytochemical class/pure compounds' name
- Method of analysis used
- Present findings

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