Sesquiterpene C15

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Like monoterpenes, these are major components of many essential oils. The sesquiterpene acts as irritants when applied externally and when consumed internally their action resembles that of gastrointestinal tract irritant. A number of sesquiterpene lactones have been isolated and broadly they have antimicrobial (particularly antiprotozoal) and neutotoxic action.

Artemisnin Santonin

Fig. 5.236 Structure of common sesquiterpenes.

Artemisnin Santonin

Fig. 5.236 Structure of common sesquiterpenes.

Sesquiterpene lactone, palasonin, isolated from Butea monosperma has anthelmintic activity (Fig. 5.237). It inhibits glucose uptake and depletes the glycogen content in Ascaridia galli.

Fig. 5.237 Structure of Palasonin.

Fig. 5.237 Structure of Palasonin.

Parthenolide (Fig. 5.238), sesquiterpene lactone, found in Tanacetum parthenium has anti-inflammatory, antisecretory and spasmolytic activities (Fig. 5.165). It also inhibits the release of serotonin through various mediators and inhibits activation of MAP kinase. It has been used in the treatment of migraine.

Arglabin isolated from Artemisia myriantha has immunomodulator activity. Inuviscolide isolated from Inula viscosa has anti-inflammatory activity. Lychnophorolide A, sesquiterpene lactone from Eremanthus eriopus is reported to be analgesic. Khusinol and khusol are sesquiterpene alcohol from Vetiveria zizanoides oil (Fig. 5.239).

h h ch2oh

Fig. 5.239 Structure of Khusinol and Khusol.

Himachalol (Fig. 5.240), a sesquiterpene alcohol obtained from hexane soluble extract of the wood of Cedrus deodara was found to have significant anti-allergic activity. The effect was comparable to disodium cromoglycate in experimental models. Jatamansone (valeranone) and nardostachone are the principal sesquiterpenes of Nardostachys jatamansi (Figs. 5.241, 5.242). Jatamansone has antihypertensive, sedative and tranquilizing activities.

Fig. 5.239 Structure of Himachalol.

Fig. 5.239 Structure of Himachalol.

Fig. 5.241 Structure of Nardostachone.

Fig. 5.240 Structure of Jatamansone.

Fig. 5.241 Structure of Nardostachone.

5.4.13.4 Diterpene: C20

These are classically considered to be resins. Taxol, the anticancer agent, is familiar example (Fig. 5.242).

o ch3

Taxol is found predominantly in the bark of T. brevifolia, but in relatively small amounts (about 0.01-0.02%). Up to 0.033% of taxol has been recorded in some samples of leaves and twigs, but generally the taxol content is much lower than in the bark. The content of some other taxane derivatives in the bark is considerably higher, e.g. up to 0.2% baccatin III. Other taxane derivatives characterized include 10-deacetyltaxol, 10-deacetylbaccatin III, cephalomannine and 10-deacetylcephalomannine.

Paclitaxel (taxol) is being used clinically in the treatment of ovarian and breast cancers, non-small-cell lung cancer, small-cell lung cancer, and cancers of the head and neck. Taxol has also been shown to bind to a second target, a protein which normally blocks the process of apoptosis (cell death). Inhibition of this protein allows apoptosis to proceed.

Pondicin and oridonin isolated from Rabdosia rubscens are anticancer. Dehydrocrotonin isolated from Croton cajucara is antileukemic and anti-ulcerogenic. Scopadulin, tetracyclic diterpene from Scopolia parviflora has antiviral activity. Ballota nigra contains diterpenes including marrubiin, 7-acetoxymarrubiin, ballotinon, ballotenol and ballonigrin.

Salvinorin A, ditepene found in Salvia divinorum is reported to be useful against alcoholic addiction (Fig. 5.243).

Forskolin is a labdane diterpene found in Coleus forskolii. It is used to raise the levels of cyclic AMP (Fig. 5.244). It resensitizes cell receptors by activating the enzyme adenyl cyclase and increasing intracellular levels of cAMP, which is an important signal carrier that is necessary for proper biological response of cells to hormones and other extracellular signals.

Fig. 5.243 Structure of Salvinorin A.

Fig. 5.243 Structure of Salvinorin A.

Fig. 5.244 Structure of Forskolin.

5.4.13.5 Triterpene: C30

This group includes common triterpenes, steroids, sterols, and cardiac glycosides.

Common triterpenes: Amyrins, ursolic acid and oleanic acid (Fig. 5.245).

cooh h3c ch3

Ursolic acid h3c ch3

Ursolic acid

OH H

OH H

CH3 H

a- amyrin

CH3 H

a- amyrin oh oh

h h3c h3c

cooh h3c h3c cooh p-amyrin Oleanoic acid

Fig. 5.245 Structure of common triterpenes.

Healianol, triterpene alcohol from Calendula officinalis has antiinflammatory activity. Triterpenoids lupeol and varunol have been isolated from the root and stem bark of Cratavea nurvala. A triterpenoid, ch cooh

3 a-hyrdoxy-D-friedoolean-1-ene has been reported from Adhatoda vasica. Galphimine-B from Galphinia glauca has sedative activity. Abrisapogenol E and abrisapogenaldacetal from Rabinia pseudoacacia are cytotoxic. Triterpenoids from Pourouma guainensis are antileshmanial. Azadirachtin (Fig. 5.246) isolated from Azadirachta indica is potent insecticidal. Nimbin, nimbinin and nimbidin are other triterpenes derived from neem.

oh oh

Fig. 5.246 Strucuture of Azadirachtin.

Fig. 5.246 Strucuture of Azadirachtin.

Saponins: See Section 2.3.10.

Sterols: fi-sitosterol, stigmasterol, taraxasterol and campesterol (Fig. 5.247).

P-sitosterol
Nimbidin And Nimbolide StructureTaraxasterol
Stigmasterol
Taraxasterol
Taraxasterol Fig. 5.247 Structure of common sterols.

Phytosterols compete with dietary cholesterol for uptake in the intestines. They have demonstrated the ability to block the uptake of cholesterol and facitilate its excretion from the body. Contradicting this, some studies have reported inefficency of morning sterols in competing with dietary cholesterol.

Phytostans (stanols)

These are saturated phytosterols. Thay are widely distributed in plants. They have cholesterol lowering activity.

Table 5.13 Terpenes from medicinal plants.

S.No

Name of the terpene

Source

1.

2-a-hydroxymicromeric acid

Terminalia chebula

2.

Absinthin

Artemisia absinthum

3.

Ajoene

Allium sativum

4.

Allicin

Allium sativum

5.

Amberttolide

Hibiscus abelmoschus

6.

Angelic acid

Angelica glauca

7.

Asarone

Acorus calamus

8.

Azadirachtin

Azadirachta indica

9.

Betulinic acid

Nelumbo nucifra, Betula utilis

10.

Calliterpenone

Callicapra macrophylla

11.

Camphor

Cinnamomum camphora.

12.

Cineol

Eucalyptus globulus

13.

Elephantopin

Elephantpous scaber

14.

Grandiflorenic acid

Aspilia mossambicensis

15.

Helenin

Inula racemosa

16.

Himachalol

Cedrus deodara

17.

Jatamansin

Nardostachys jatamansi

18.

Kaurenoic acid

Aspilia mossambicensis

19.

Menthol

Mentha spicata

20.

Myricadiol

Myrica nagi

21.

Palasonin

Butea frondosa

22.

Safranal

Crocus sativus

23.

Salacinol

Salacia reticulata

24.

Santonin

Artemisia santonica

25.

Stemmin C

Solenostemma arghel

26.

Stemnoside A

Solenostemma arghel

27.

Stemnoside B

Solenostemma arghel

28.

Thymol

Thymus vulgaris

29.

Valerianic acid

Valeriana officinalis

5.4.14 Withanolides

These are a group of naturally occurring oxygenated ergostane type steroids having lactone in side chain and 2-en-1-one system in ring A (Fig. 5.248).

Withanolides isolated from the leaves of Withania somnifera have shown significant antitumor and immunomodulator activity. Coagulin F and coagulin G isolated from Withania coagulens have anti fungal properties. 3 beta-hydroxyl 2, -3-dihydrowithanolide F, present in fruits, have significant hepatoprotective and anti-inflammatory activity. Withaferin A (Fig. 5.176) and withanolide E have immunosupressant activity.

Withanolides of W. somnifera

Withanolides were first isolated from W. somnifera hence the name withanolide. Chemically, they are a group of naturally occurring oxygenated ergostane type steroids having lactone in side chain and 2-en-1-one system in ring A. Velde and Lavie reported 1a, 3p, 20-trihydroxy witha-5, 24-dienolide from W. somnifera chemotype 3. 7a, 27-hydroxy-1-oxo- witha-2, 5-24-trienolide and 7a, 27-dihydroxy-1-oxo- witha-2, 5-24-trienolide have been reported from W. somnifera chemotype 3.

Withanolide S has been reported from from the leaves of W. somnifera. Kirson, Glotter and Withanolides Q and R have been reported from the offspring of Indian chemotype 1 and 3 of W. somnifera. Withasomnilide, withasomniferabolide, somniferanolide and somnwithanolide have been reported from the stem bark of W. somnifera. A new compound, chlorohyrdin 11 has been reported. 27-O-glucosides (sitoinoside IX and X) were reported from from roots of W. somnifera. Withasomidienone have been reported. The withanolides reported from W. somnifera are tabulated below:

Table 5.14 Major withanolides of W.somnifera.

SNo

Name

Pharmacological activity

1.

20|3-hydroxy-1-oxo-(22R)-witha-2,5,24-trienolide, witha-coagulin and a known withanolide, 17|3-hydroxy-14a, 20a-epoxy-1-oxo-(22R)-witha-3,5,24-trienolide

2.

27-deoxywithaferin A

3.

27-hydroxy withanolide A

Table 5.14 contd...

4.

3fi-hydroxy-2,3-dihydro withanolide F

Hepatoprotective

5.

3-p-hydroxy-2,3-dihydro-withano]ide

Antibacterial, antitumor, immunomodulator and anti-inflammatory

6.

4p-hydroxy-withanolide

7.

Ashwagandholine

8.

chlorohyrdin II

9.

Coagulin

10.

Compound WS-1

Hypno-sedative

11.

Compound WS-2

Antibacterial

12.

Jaborosalactone

13.

Sitoindside-IX,X

Immunomodulator and C.N.S effects

sominolide, soinone, withasomnilide, withasomnifer-abolide, somniferanolide and somnwithanolide

14.

Somniferanolide

15.

Somnwithanolide

16.

Withacoagin

17.

Withaferinil

Antitumor

18.

Withaniol

19.

Withanoferin

20.

Withanolide D

Antitumor

21.

Withanolide E

Antifeedent

22.

Withanolide Q and R

23.

Withanolide S and T

24.

Withanolide sulfoxide

Antitumor

25.

Withanolide Y

26.

Withanolide Z

Not confirmed

27.

Withanolide-5 ,20a,(R)-dihydroxy-6a,7a- epoxy-1-oxo-5 a -with a-2,24-dienolide

Immunomodulator

28.

Withanone

Antitumor

29.

Withanoside

30.

Withaphysanolide A

31.

Withasomidienone

32.

Withasomniferabolide

33.

Withasomnilide

34.

Withastramonolide

OH

Withaferin A

Structure Withanone
OH

27-deoxywithaferin A

27-deoxywithaferin A

Structure Withanone Structure Withanone

OH OH

Sitoindoside IX

H3 OPalmitoyl

H3 OPalmitoyl

Structure Withanone

OH OH

OH OH

OH OH

Sitoindoside X Fig. 5.249 Structure of major withanolides of W.somnifera.

Table 5.15 Withanolides from other medicinal plants.

S. No

Name of the withanolide

Source

1.

20beta-hydroxy-1-oxo-(22R)-witha-2,5,24-trienolide; Withacoagulin; 17beta-hydroxy-14-alpha, 20alpha-epoxy-1-oxo-(22R)-witha-3-,5,24-trienolide

Withania coagulan

2.

6alpha,7alpha-epoxy-5alpha,17beta-dihy-droxy-1-oxowitha-2,24-dienolide and 17-Epiacnistin-A

Discopodium penninervium

3.

Bracteosin A, bracteosin B and bracteosin C

Ajuga bracteosa

4.

Chantriolides A and B

Tacca chantrieri

5.

Cilistadiol, cilistepoxide and cilistol-A

Solanum sisymbiifolium

Table 5.15 contd...

S. No

Name of the withanolide

Source

6.

Cinerolide, 24,25-dihydrowithanolide S, visconolide, physalactone, withanolide S and 4beta-hydroxywithanolide E

Physalis cinerascens

7.

Daturalactone-4; Nic-3 (hyoscyamilactol); 16alpha-acetoxyhyoscyamilactol

Hyoscyamus niger

8.

Daturametelins C, D, E, F and G

Datura metel

9.

Ixocarpalactone A, 2,3-dihydro-3ß- methoxyixocarpalactone A,2,3-dihydro-3ß-methoxyixocarpalactone B, 2,3-dihydroixocarpalactone B, and 4ß,7ß,20R-trihydroxy-1-oxowitha-2,5-dien-22,26-o!ide

Physalis philadelphica

10.

Physachenolides A - E.

Physalis chenopodifolia

11.

Physagulins L, M and N, Physagulin D and quercetin 3-O-rhamnosyl-(1-->6)-galactoside

Physalis angulata

12.

Pplantagiolides A-E and chantriolide A

Tacca plantaginea

13.

Subtrifloralactones A-E,F-L, new C-18 oxygenated withanolide, 13ß-hydroxymethylsubtrifloralactone E and phila-delphicalactone A

Deprea subtriflora

14.

Two new withanolide glycosides and 18-acetoxywithanolide D and 18-acetoxy-5,6-deoxy-5-withenolide D

Dunalia brachyacantha

15.

Withaferin A and witharistatin

Withania aristata

16.

Withangulatin A and withangulatin I

Physalis angulata

17.

Withanolide 1 and 2

Jaborosa caulescens (var. caulescens and var. bipinnatifida)

Withanolide-7

Physalis minima

18.

Withanone

Discopodium penninervium, Exodeconus maritimus, Withania somnifera

19.

Witharifeen and daturalicin

Datura innoxia

Vasodilator Medicinal PlantsVasodilator Medicinal Plants
ixocarpalactone A
Structure Withanone
Daturametelin Fig. 5.250 Structure of bioactive withanolides.

5.4.15 Xanthones

These are phenolic product of a triketide precursor and benzoid unit. Swerchinin from Swertia chirata lowered blood glucose in normal and streptozocin induced mild and severe diabetes in rats (Fig. 5.251). The effect of swerchirin was comparable to tolbutamide. Swerchirin has demonstrated a protective effect on hematopoiesis in 6-Co-irridiated mice. S.chirata also contains a novel dimeric xanthone, chiratanin.

H3C\

H3C\

oh o

Gentiacaulin isolated from Swertia kochiana has vasodilator activity. Gentisin (Fig. 5.252) and isogentisin (Fig. 5.253) from Gentiana lutea has significant mutagenic activity. Gentisein (Fig. 5.254) is also isolated from G. lutea.

Chirata Structure

Fig. 5.254 Structure of Gentisein.

oh o

Fig. 5.254 Structure of Gentisein.

The ethanol extract of the bark of Garcinia dulcis furnished five xanthones; garciniaxanthone showed inhibitory effects on the growth of P. falciparum with IC50 value of 0.96 mg/ml85.

Table 5.16 Xanthones from medicinal plants.

S.No

Name of the xanthone

Source

1.

Decussatin

Swertia decussata

2.

Dixylopyranoside

Swertia thomsonii, S. franchetiana

3.

Gentiacaulein

Gentiana kochiana

4.

Gentiakochianin

Gentiana kochiana

5.

Gentisin

Gentiana lutea

6.

Swerchirin

Swertia chirayita, S.japonica and S. mussotii

7.

Swertiapuniside

Swertia punicea

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