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Sustainable Production > Secondary Metabolites > Flashcards

Secondary Metabolites Flashcards

1
Q

What are secondary metabolites?

A

Plants produce a large and diverse array of organic compounds that appear to have no direct function in growth and development - no role in photosynthesis, respiration, solute transport, translocation, protein synthesis, etc…

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2
Q

What are the three major ecological functions of secondary metabolites?

A
  • Protect plant from herbivory and being infected by microbial pathogens
  • Serve as attractants for pollinators and seed-dispersing animals (smell, colour and taste)
  • Function as agents of plant-plant competition and plant microbe symbioses
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3
Q

What are the three chemically-distinct groups that you can divide secondary metabolites into?

A

Terpenes
Phenolics, and
Nitrogen-containing compounds

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4
Q

What are terpenes?

A

Oily substances composed of ISOPRENE units
They often have a strong odor and may protect the plants that produce them by deterring herbivores and by attracting predators and parasites of herbivores.

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5
Q

What is the largest group of secondary metabolites?

A

Terpenes - 25,000 different forms identified in higher plants alone

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6
Q

Are terpenes unique to higher plants?

A

Not unique to higher plants – also synthesized in animals, bacteria, fungi and algae

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7
Q

What are the industrial uses of terpenes?

A

Industrial uses – essential oils, antioxidants, anticancer drugs, contraceptives

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8
Q

What are isoprene units (of terpene)?

A

Terpenes are derived from the UNION of five-carbon elements that have the branched carbon skeleton of isopentane (sometimes referred to as isoprene units as terpenes decompose at high temperatures to give isoprene).

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9
Q

Are terpenes soluble in water?

A

No, soluble in ethanol

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10
Q

What are the 4 types of terpenes we can talk about

A

monoterpenes (which have two C5 units)
sesquiterpenes (which have three 5C units)
diterpenes (which have four 5C units),
triterpenes, tetraterpenes and polyterpenoids.

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11
Q

What are essential oils?

A

mixtures of volatile monoterpenes and sesquiterpenes that lend a characteristic smell to the foliage

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12
Q

What properties do essential oils have?

A

They have insect-repellent properties and are frequently found in glandular hairs that project outwards, ‘advertising’ the toxicity of the plant to potential herbivores.

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13
Q

What is rose oil?

A

essential oil extracted from the petals of various types of rose

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14
Q

What are the three main constitients of rose oil?

A

Geraniol (acyclic monoterpene alcohol)
Citronellol (a monoterpene alcohol)
Damascenone (cyclic monoterpene ketone)

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15
Q

What countries are the main are the main producers of rose oil

A

Bulgaria and Turkey, supplying 80 – 90% of this product to the world market.

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16
Q

How much of rose flowers are used to process rose oil

A

90% of rose flowers are processed to rose oil
5 – 6% of rose flowers are processed to rose concrete
3 – 4% of rose flowers are processed to rose water

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17
Q

From what do we extract rose oil from?

A 
Rose family Rosaceae - 
Damask rose
Gallic Rose
Musk Rose
Rosa fedtschenkoana
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18
Q

How many damask rose petals are needed to produce one kg of rose oil?

A

3000 to 4000 kg damask rose petals

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19
Q

What are the main essential oils in the market

A

Mint Oil (most in global market - 344 million)
Rose Oil
Lavender Oil
Sandalwood Oil

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20
Q

What is Azadirachtin?

A

One of the most powerful natural deterrents to insect feeding is a limonoid, triterpene (C30), extracted from the Neem tree.

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21
Q

What is a neem tree?

A

It is grown in the tropics for shade, reforestation and the production of raw materials for natural insecticides and medicines, can extract Azadirachtin.

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22
Q

How does Azadirachtin repell insects

A

It is used as a commercial insect growth regulator that controls the metamorphosis process as the insect passes from the larva stage to the pupa stage - reduces the level of the insect hormone Ecdysome ( cannot develop into adults)

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23
Q

What does the effective dose (ED50) of azadirachtin mean?

A

causes 50% inhibition of feeding

24
Q

What is an Ecdysome?

A
  • major steroid hormone in insects and plays essential roles in coordinating developmental transitions such as larval moulting and metamorphosis through its active metabolite 20-hydroxyecdysone
25
Q

What are phytoecdysones?

A
  • plant-derived ecdysteroids, first isolated from the common fern, are a group of plant steroids (terpenes) which have the same basic structure of insect moulting hormone.
26
Q

What is Taxol?

A

Taxol is a diterpene widely used in treatment of cancer. It was first isolated from the bark of the Pacific Yew (Taxus brevifolia).

27
Q

What is Taxol and when was it first isolated?

A

Taxol is a diterpene widely used in treatment of cancer. It was first isolated from the bark of the Pacific Yew (Taxus brevifolia).

28
Q

What is the benefit of taxol?

A
  • Pacific yew bark extract was the only candidate to be found to inhibit the groth of cancer cell cultures.
  • Active ingredient, taxol, isolated and approved for clinical trials in 1984. In 1988, was found to be effective against ovarian cancer.
29
Q

What is the problem with taxol?

A

Extremely limited supply – synthetic methods at best produced 0.5g of taxol from a single tree, one that had taken 200 years to reach maturity.
It would take over 360,000 trees to produce enough taxol to treat all ovarian cancer patients in USA alone.

30
Q

There was a solution found to deal with the limited supply of taxol - what was it?

A
  • France of a related chemical (10-deacetylbaccatin, or 10-DAB) that could be used to synthesise Taxol and that could be extracted in large quantities, not from the entire tree but just from the needles of the English Yew, Taxas baccata.
  • Taxol is now the best-selling cancer drug ever manufactured, with annual sales peaking at $1.6 billion in 2000.
31
Q

Terpenes as Contraceptives - SUCCESS

A
  • Diosgenin - phytoestrogen, plant-based estrogen, that can be chemically converted into a hormone called progesterone.
  • used in the 1940s to manufacture Progesterone (injected), and then, later, Norethindrone (oral)
  • Diosgenin was used to make the first birth control pills in the 1960s
32
Q

From what do you extract diosgenin?

A

extracted from the tubers of Dioscorea wild yam, such as the Kokoro from Mexico

33
Q

Terpenes as Contraceptives - FAILURE

A
  • Cotton seeds (Gossypium sp), contain high concentrations of the sesquiterpene, Gossypol. - – Gossypol causes male infertility in humans and mammals by inhibiting spermatogenesis.
34
Q

What were the toxic side effects of gossypol?

A
  • Extensive trials in China from 1970s to 1980s involving 8000 men.
  • Toxic side effects – kidney malfunction in up to 10% leading to hypokalemia (loss of potassium).
  • Irreversible infertility in over 20% of the men.
35
Q

What are plant phenolics?

A

Plant phenolics are a chemically heterogenous group of nearly 10,000 individual compounds, produced by plants mainly for protection against stress

36
Q

What are the roles of plant phenolics in plant metabolism?

A

Mechanical support (lignin)
Pollinator attraction and fruit dispersal (anthocyanins)
UV protection (flavonoids)
Defence against herbivory and pathogens (tannins)
Inhibition of growth by other plants (various)

37
Q

Furanocoumarins and phototoxicity

A

Many simple phenolic compounds have important roles in plants as defences against insect herbivores and fungi.

The phototoxicity of FURANOCOUMARINS are one significant example.

Activated by UV-A light, these compounds insert themselves into the double helix of DNA, bind to the pyrimidine bases, cytosine and thymine, and block transcription, repair leading to cell death……

……they cause significant chemical burns!!!

38
Q

Furandocourmarns in grapefruit

A

Furanocoumarns in Grapefruit

39
Q

What are anyhocyanins

A

Anthocyanins : Coloured pigments of plants provide visual clues to attract pollinators and seed dispersers.

40
Q

Two types of anthocyanins

A

Two principal types:

(a) Carotenoids (yellow, orange and red terpenoids - plastidic)
(b) Flavonoids (red, pink, purple and blue colours – vacuolar)

41
Q

Flavones and Flavonols

A

Flavones and Flavonols absorb light at shorter wavelengths than anthocyanins, so are not visible to the human eye.

They are visible to bees and other insects, which see farther into the UV range of the visible spectrum than humans. Thought to indicate location of pollen and nectar.
Flavones and flavonols are not restricted to flowers but are present in the leaves of all green plants. They play a key role in the photoprotection of plant cells from UV-B radiation

42
Q

Allelopathy

A

Allelopathy

43
Q

Tannins

A

Phenolics and Herbivory
Tannins

(a) Large molecular weight condensed tannins
(a) Smaller molecular weight hydrolyzable tannins

44
Q

Tannins

A

Tannins are general toxins that can reduce growth and survival of many herbivores when added to their diet. In addition, tannins act as feeding repellents.

45
Q

What are nitrogen containing compounds

A

A large variety of medicinally important secondary metabolites have nitrogen in their structure. Included in this category are such well-known antiherbivore defences as alkaloids and cyanogenic glycosides.

46
Q

What are alkaloids?

A

Alkaloids: Found in approx. 20% of all plant species. The nitrogen atom is usually part of a heterocyclic ring, a ring that contains both nitrogen and carbon atoms. They are best known for their striking pharmacological effects on vertebrate animals.

47
Q

Major types of alkaloids

A

Tropane - > cocaine (stim of nervous systehm

48
Q

What are other nitrogenous protective compounds found in plants other than alkaloids

A

cyanogenic glycosides. These are not toxic themselves but when broken down may produce hydrogen cyanide.

49
Q

Larkspur

A

Alkaloids

Larkspur, Poison Weed
The LD50 of total toxic alkaloid for ‘Tall Larkspur’ has been shown experimentally to be between 25 and 40 mg/kg body weight.
As little as 17 g/kg body weight of the green plant of D. barbeyi (Tall Larkspur) is lethal to cattle.

50
Q

Tall Larkspur

A

‘Tall Larkspur’ consumption in cattle may range from virtually nothing in the pre-flower stage to as much as 30 percent of the animal’s diet when the plant is in the flowering stage. There is a “toxic window” of time when cattle find tall larkspur increasingly palatable, and the plants contain significant total toxic alkaloids.

51
Q

Aconite, Monkshood

A

Highly toxic, diterpenoid alkaloids including aconitine, mesaconitine, napelline and hypaconitine form the principal toxins in monkshood. All species of monkshood including cultivated species (A. napellus) should be considered toxic to animals and humans.
Although there is no extensive documentation of the toxic dose of monkshood, horses have been reported to be fatally poisoned after eating 0.075 percent of their body weight in green plant

52
Q

Poison Hemlock, European Hemlock Spotted Hemlock, California Fern

A

At least eight piperidine alkaloids have been found in various parts of the plant. Large doses of these alkaloids cause skeletal muscle stimulation followed by neuromuscular blockade and paralysis similar to that caused by nicotine on the central and peripheral nervous systems.

Cattle have been fatally poisoned by eating as little as 0.5 percent of their body weight of green hemlock.

53
Q

Water Hemlock, Cowbane, Poison Parsnip

A

The principal toxin is Cicutoxin, a highly unsaturated (diol), which is one of the most toxic naturally occurring plant compounds known.

The toxin is concentrated in the tuberous roots, but all parts of the plant including the fluid found in the hollow stems are toxic.
All animals, including humans, can be fatally poisoned by eating as little as 50 to 110 mg/kg body weight of the green water hemlock plant.

54
Q

Wild Blue Flax

A

The principal toxin is the cyanogenic glycoside, linamarin (lotaustralin). Highest concentrations of the glycosides are found in the seedling tops and seeds (910 mg/100 g). There however, appears to considerable variation in the quantity of cyanogenic glycoside present depending upon the species and growing conditions of flax.

55
Q

Western Choke-Cherry

A

Choke-cherries contain two cyanogenic glycosides-amygdalin, which is commonly found in the seed, and prunasin, which is found in the leaves, bark, and shoots.
Note - The larger succulent leaves are the most toxic with concentrations of cyanogenic glycosides reaching 368 mg/100 g of fresh leaves.
Ruminants consuming 25 percent of their body weight in green leaves are likely to suffer fatal cyanide poisoning.

Sustainable Production (7 decks)

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