Natural Product Chemistry

Question 1

Phenols

Answer 1

• Carbolic acid (Phenol), single hydroxyl group linked to a benzene ring
• Phenolic acids are characterized by a carboxyl group substituted on a phenol.
• Salicylic acid- used in topical treatment of acne and precursor to aspirin

Question 2

Polyphenols

Answer 2

composed of greater than 1 phenolic unit, lacks nitrogen

Question 3

Cinnamic Acids

Answer 3

• Plants produce six common cinnamic acids: cinnamic acid, pcomaric acid, caffeic acid, ferulic acid, 5 hydroxyferulic acid and sinapic acid.
• These are considered to be ubiquitous across most plant species, with at least three being found in each species.

Question 4

Flavones

Answer 4

phenolic structures with 1 carbonyl group (as opposed to

the 2 carbonyls in quinones)

Question 5

Flavonol

Answer 5

phenolic structures with 1 carbonyl group and add a 3 -hydroxyl group

Question 6

Flavonoid (chemically)

Answer 6

phenolic structures with 1 carbonyl group and add a 3 -hydroxyl group and also
hydroxylated, but as a C6-C3 unit linked to an aromatic
ring

Question 7

Flavenoid:

Answer 7

-These compounds occur as plant pigments often yellow or orange (flavus = yellow)
-They are universal within the plant kingdom
-It is likely that one of their main roles in nature is as color attractants to insects and birds, or to affect the taste of plants (some are bitter and astringent and some are intensely sweet)
-Flavonoids have important dietary significance because,
being phenolic compounds they are strongly antioxidant
-Many disease states are induced or aggravated by free radicals such as superoxide. Flavonoids have the ability of scavenge these oxidizing species
-Foods rich on flavonoids have been proposed to be important on ameliorating diseases such as cancer and hearth disease
-Flavonoids occur both free (aglycone) and as glycosides
-Flavonoids are important components of the human diet. Average consumption is estimated at approximately 1 g/per day/per person
-Synthesized by plants in response to infection

Question 8

Catechins

Answer 8

Shown some antibacterial activity against Strep, Shigella and inactivating the cholera toxin

Question 9

Isoflavones

Answer 9

are active against variety of microorganisms and have been used successfully to prevent schistosomal infection

Question 10

Dietary antioxidants

Answer 10

◦ Blackberries (anthocyanins)
◦ Grapes
◦ Cocoa
◦ Blueberries
◦ Pomegranates
◦ Tomatoes (lycopene)
◦ Strawberries
◦ Tumeric (cucurmin)

Question 11

Anthocyanins

Answer 11

superoxide radicals
scavenging effects in vitro and in vivo.
They have been associated with
collagen-stabilizing activity.

Question 12

Resveratrol

Answer 12

Flavenoids
Given that it is present in grape berry skins but not in
flesh, white wine contains very small amounts of
resveratrol, compared to red wine
The concentrations in the form of trans- and cis- isomers
of aglycone and glucosides are subjected to numerous
variables.

Question 13

Acai Berry

Answer 13

Euterpe oleraceae, Rich in polyphenols

Question 14

Quinones

Answer 14

• Responsible for browning of veggies and fruits when cut and dying properties of henna
• Quinones provide a source of stable free radicals – and can inactivate proteins by irreversible complexing with nucleophilic amino acids
• Antibacterial targets: surface exposed adhesins, cell-wall polypeptides, & membranebound enzymes

Question 15

Tannins

Answer 15

-Polymeric phenolic compounds with the ability to “tan” leather (astringent properties)
-Found in almost every plant part
-Formed by condensations of flavan derivatives or by polymerization of quinone units
-Act by complexing with proteins via hydrogen bonding,
hydrophobic effects, and covalent bond formation inactivating microbial adhesins, enzymes, and cell envelope transport proteins
-Tannins represent a very large group of polyphenolic
natural products
-They are widely distributed in the bark, insect galls, leaves, stems and fruits
-They are the main constituent for astringency
-They have the ability to precipitate proteins into insoluble complex (used to “tan” animal hides

Question 16

Coumarins

Answer 16

• Smells like freshly cut hay
• Examples of coumarins with such biological activity include aesculetin, scopoletin, and umbelliferone.
• most commonly found in the Apiaceae (carrot), Rutaceae (citrus), Asteraceae (daisy) and Fabaceae (bean) families.
• Best known for their anithrombotic, antiinflammatory, and vasodilatory activity
• Coumarins stimulate macrophages – which could help clear infections
• Coumarin has also been used to prevent recurrences of viral cold sores caused by HSV-1

Question 17

Psoralens

Answer 17

Coumarins that have a furan
ring
Readily absorb light
Typical in Rutaceae (citrus) and Apiaceae (carrot) families
Carcinogenic and mutagenic
Used in treatment of vitiligo (melanin deficient skinpatches), eczema and psoriasis

Question 18

Furanocoumarins

Answer 18

Furanocoumarins have furan ring at C-6 C-7 or C-7 C-8.
Psoralen have photosensitizing activity utilized on the
treatment of psoriasis in combination with UV light
(PUVA). It is also used to promote skin pigmentation in
vitiligo

Question 19

Terpenoids and Essential Oils

Answer 19

Terpenes (C10H16) – also occur
as di-, tri-. tetra-, hemi-, and
sesqui-terpenes
Terpenoids contain additional
elements (usually oxygen)
Responsible for plant
fragrance
Exhibit activity against:
viruses, fungi, bacteria, and
protozoa

Question 20

Alkaloids

Answer 20

Have a cyclic nitrogen, best known for psychoactive effects, some can intercalate with DNA

Question 21

Pyridine alkaloid:

Answer 21

Nicotine from Nicotiana tabacum

Stimulent component to tobacoo

Question 22

piperidine alkaloid

Answer 22

Coniine (conium maculatum)- poison socrates was forced to drink
Arecoline (Areca catechu)- betel nuts addictive due to presence of this stimulant

Question 23

Pyrrolizidine alkaloid

Answer 23

Senecionine from sympytum officinale- hepatotoxic properties

Question 24

Phenylalkylamine alkaloids

Answer 24

Ephedrine from Ephedra sinica (Ma Huang)
◦ CNS stimulant, vasoconstrictor, and bronchodilatory
◦ Mescaline from Lophophora williamsii (peyote)
◦ Contributes to hallucination & vivid dream effects of peyote

Question 25

Quinoline alkaloids

Answer 25

Quinine from Cinchona

Question 26

isoquinoline alkaloids

Answer 26

Morphine from Papaver somniferum (opium poppy)

Question 27

Indole alkaloids

Answer 27

Reserpine from Rauvolfia serpentina (snake root)
◦ antihypertensive
◦ Inogaine from Tabernanthe iboga (iboga)
◦ Hallucinogenic and anticonvulsant

Question 28

Tropane alkaloids

Answer 28

Hyoscamine/atropine from Atropa belladonna (deadly nightshade)
◦ Anticholinergic, mydriatic (pupil dilation), and used to treat acute cardiac arrhythmias

Question 29

Xanthine alkaloids

Answer 29

◦ Caffeine from Coffea arabica (coffee)

◦ CNS stimulant and diuretic

Question 30

Imidazole alkaloids

Answer 30

Pilocarpine from Pilocarpus jaborandi (jaborandi)

◦ Cholinergic and used to treat glaucoma, causes miosis (pupillary constriction)

Question 31

Lectins and Polypeptides

Answer 31

Peptides – often +-charged with disulfide bonds
 May act by forming ion channels in microbial membrane or competitive inhibition of adhesion of microbial proteins to host receptors
 Thionin peptides (45-50 a.a. long) found in barley and wheat are toxic to yeast and gram positive bacteria
 Fabatins (found in fava beans) are 47a.a. long and
inhibit gram + and – bacteria (Zhang & Lewis, FEMS Microbiology Letters, 2006)

Question 32

Glycosides

Answer 32

Glycoside = general term for natural product bound to a sugar
◦ 2 parts: aglycone (terpene, coumarin, flavonoid, etc) + sugar
Cyanide Glycosides
◦ Amygdalin found in seeds of Prunus species
◦ Cyanide glycosides found in cassava tuber (Manihot esculenta) yield HCN

 Many glycosides remain bio-inactive until they are hydrolyzed and the aglycone is released “prodrugs’
 Classification of glycosides is based on the nature of the aglycone
 This is a heterogeneous group with little in common besides their physicochemical properties, e.g. they are very hydrophilic, and hygroscopic