S1 L4 Evaluation of plant drugs

1. Botanical B. Microscopy

Cell inclusions

Anna Drew

Cell inclusions• Parenchyma cells

• Contain characteristic contents of living protoplasts» Eg nucleus, cytoplasm, vacuoles, plastids,

mitochondria

• Not diagnostically useful

• Non-protoplasmic components• Classified as ‘ergastic’ substances

» Starch» Protein» Oil» Crystals

• Very useful for identification

1. CALCIUM OXALATE

• Crystals may be reserve or waste products of cellular activity

• Oxalate ions removed in making crystals• Don’t know why they arise (could be pH)• Or why they are found in particular locations

(vascular tissue) and not others (near veins)

• Clearing agents:– Chloral hydrate solution to remove chlorophyll (cell walls

etc remain)– Show in crossed polaroids

• Comment on size, shape, frequency

(a) Prisms

• One prism per parenchyma cell• Cells form a sheath around fibres in vascular bundle

• Eg cascara, senna, liquorice

Hyoscyamus leaf

Twin crystals

Calcium oxalate of Cassia acutifolia (senna) leaflet (viewed under high power)

Note – cluster crystals also present in senna leaflet

(b) Clusters & rosettes

• Microrosettes in Umbelliferae eg anise, fennel

Eg Senna Cascara Stramonium

Eg Rhubarb rhizome

Calcium oxalate of Datura Stramonium leaf (viewed under high power)

Calcium oxalate of Datura stramonium leaf (viewed under low power)

(c) Needles (acicular)

• Occupy the whole parenchyma cell• Next cell contains none

• Eg ipecacuahna, squill

Calcium oxalate of Cephaelis ipecacuanha rhizome (viewed under high power)

(d) Microsphenoids (crystal sand)

• Very small• Adjacent cells don’t store them

• Eg belladonna

Calcium oxalate of Atropa belladonna leaf (viewed under high power)

2. CALCIUM CARBONATE

• Not as common as calcium oxalate• Eg cannabis cell

Calcium carbonate deposit

3. STARCH GRAINS

• More common

• Occur as discrete grains

• Commonly show layering of amylose & amylopectin around a point ‘hilum’

• Found in parenchyma of pith, cortex, vascular tissues, fruits, cotyledons & seed endosperms

• Generally not found in leaves – transported out

• Staining:» Dilute glycerin» Chloral hydrate to dissolve pigments

» * I2 blue-black stain

» * Polarised light – not bright

‘Maltese cross’ effect (page 15 microscopy notes)

* Characteristics of plant starch

• Shape

• One shape will be dominant or characteristic of a plant Eg

» Polyhedral – maize starch» Ovoid with a few round – potato» Sac shape – ginger

• Aggregation

• Can be single, 2, 3 -> multicompound grain» Eg ipecacuanha

• Size» Rice 6 µm» Potato 45-70 µm

• Hilum

• Striations• Present or absent• Layers of amylose and amylopectin

• Frequency• Absent – rare – abundant (90% of plant material)

• Location• Where they are found Eg root, rhizomes, seeds etc• May just be in specific tissues Eg pith, cortex, perisperm

Single point

Line in a grain Cleft Stellate

Punctate (hole)

Potato starch grains (viewed under high power)

Maize starch grains (viewed under high power)

Cephaelis ipecacuanha rhizome starch

4. PROTEIN

• Indicative of seed material• Diagnostic feature:

» Picric acid stains protein yellow» Allow a few minutes to stain, wash away rest

Amorphous

Crystalloid protein

Amorphous protein

Globoid

Calcium oxalate

Phosphorus protein

Aleurone Eg Linseed

5. OILS, FATS

• May float out in stain to below coverslip

• Fixed oil– Esters of glycerol

» Eg linseed, olive

• Volatile (essential) oil– Look the same

– Turpine and hydrocarbons

» Eg peppermint

– Can smell

• Staining:– Sudan III, Tincture of Alkanne

• Some plants contain so much oil that it needs to be removed to see other structures

– Light petroleum removes fat

– Mix, decant off, repeat several times, then can stain

Globules

6. MUCILAGE

• Sometimes present• Has to be stained to be seen

• Staining:– Ruthenium red -> pink

• Eg senna leaves