GeraniumsOnline   

                                               

 

 

SOME THOUGHTS ON SCENTED GERANIUMS – Part 1 Wayne Handlos

                              Molecules of Essential Oils

 “The scent of geranium leaves is not a subject for logic, only a cause of delight.”

                                            -  The Joy of Geraniums by Helen Van Pelt Wilson.


Scented geraniums/pelargoniums are known for the fragrance of their foliage. The scented

compounds are generally essential oils – volatile to varying degrees – produced in the glandular

hairs (trichomes) which clothe the leaves and stems in varying densities.


Most scented geraniums/pelargoniums are in the taxonomic section (§) called Pelargonium.

These plants can become shrub-like with woody stems under favorable conditions. While their

 flowers are neither large nor showy, the plants are easy to grow and to propagate. The species

in this section include:

P. betulinum, P. capitatum, P. citronellum, P. cordifolium, P. crispum, P. cucullatum,

P. denticulatum, P. englerianum, P. glutinosum, P. graveolens, P. greytonense, P. hermanniifolium,

P. hispidum, P. panduriforme, P. papilionaceum, P. pseudoglutinosum, P. quercifolium,

P. radens, P. ribifolium, P. scabroide, P. scabrum, P. sublignosum, P. tomentosum, P. vitifolium.


The other group of widely recognized scented geraniums is in section Reniformia and includes

the following species:


P. abrotanifolium, P. album, P. dichondrifolium, P. exstipulatum, P. x fragrans, P. ionidiflorum,


P. odoratissimum, P. reniforme, P. sidoides.

This is a group of small-leaved, herbaceous or small woody shrubs which are easy to grow.
 

Flowers are generally small, borne in open, few-flowered inflorescences.

There are a number of other species with scented leaves including the following: P. mollicomum,

P. worcesterae, P. x hortorum (zonal geraniums), P. endlicherianum, P. fulgidum, P. grossularioides,

P. grandicalcaratum among others.

Commercially, geranium oil or rose geranium oil is distilled (extracted) from the leaves and stems of

"rose geraniums". Over 120 volatile constituents have been

identified in geranium oil. This oil is used cosmetically – in perfumes, scenting soaps and lotions, etc.

Because of its similar fragrance and lower cost it is used as a substitute for real "rose oil" or attar of roses.

Geranium oil has been produced in a variety of locations over the years including

Reunion, China, Egypt, India, Morocco, Algeria, Kenya, France, Corsica, Tunisia, Congo, Tanzania, Madagascar,

South Africa, Spain, Portugal and Brazil. It takes about 300-350 kg of plant material (leaves and stems) to produce

0.3 to 0.7 kg of oil. On a per hectare basis a very productive field can be expected to produce about 45 kg of oil

per hectare.

There are several different cultivars used in the production of geranium oil. The better-known ones include: ‘Rosé’,

or cultivars named for the country of origin (Algerian, Tunisian, Bourbon, Reunion, Egyptian), or a new one from tissue

culture called ‘Narmada’. The following list shows some of the primary constituents of the fragrances produced by

different species and cultivars. [Most information is from M. Lis-Balchin, 2002, Geranium and Pelargonium. The letter "L"

indicates results from J.Y.Y.

 Lalli’s dissertation on essential oils in Pelargonium spp.]

Rosy scents

P. capitatum – α pinene, myrcene, citronellol, citronellyl formate, geranyl formate, β caryophyllene, guaia-6-9diene, germacrone D;

another analysis – L viridiflorol - 24-36.6%; another selection – citronellyl formate (37.1%), citronellol (9.9%), furopelargone B (6.1%)

‘Attar of Roses’ – linalool, isomenthone, citronellol, geraniol, citronyllyl formate, guaia-6-9-diene

‘Rosie’ – isomenthone, citronellol, geraniol, citronellyl formate, geranyl formate, guaia-6-9-diene

P. radens – isomenthone, citronellol; another analysis – L isomenthone (84.5%)

P. graveolens – linalool, isomenthone, citronellol, geraniol, citronellyl formate; another – L isomenthone (65.8%, 83.3%)

‘Rober’s Lemon Rose’ – linalool, isomethone, citronellol, geraniol, citronellyl formate, β caryophyllene

Minty

P. tomentosum – menthone, isomenthone; another analysis - L menthone (36.1-41.1%), isomenthone (49.356.6%)

‘Chocolate Tomentosum’ – α phellandrene, menthone, isomenthone

‘Lady Plymouth’ – isomenthone

Peppery pungent

P. vitifolium – citronellol, citronellic acid; another analysis – L citronellic acid (74.4%)

P. papilionaceum – citronellic acid, geranic acid; another analysis – L citronellic acid (96.2%)

 Citrusy

P. citronellum – citronellol, geranial; another analysis – L geranic acid (36%), neral (17.4%), geranial (27.2%)

P. crispum variegatum – citronellol, geranial and other sesquiterpenes

P. scabrum – terpinen -4-ol, citronellol, geranial, (other sesquiterpenes); (L 14 hydroxy β caryophyllene (27.9%)

‘Lemon Fancy’ – neral, geranial (and other sesquiterpenes)

Pungent/camphoraceous

P. glutinosum – α phellandrene, p-cymene, limonene, hexanyl butyrate, sesquiterpenes (L caryophyllene (6.3%), spathulenol (6.9%),

viridiflorol (8.9%)

P. x fragrans – α pinene, limonene, fenchone, methyl eugenol

P. odoratissimum – fenchone, isomenthone, piperitone, methyl eugenol

P. exstipulatum – α thujene, α pinene, limonene, other sesquiterpenes

P. quercifolium – β pinene, α terpineol (L p-cymene (54.9%), viridiflorol (13%), spathulanol (5.9%); another selection –

viridiflorol (24-36.6%)

‘Clorinda’ – β pinene, α phellandrene

‘Copthorne’ – α thujene, β pinene, fenchone, β caryophyllene

‘Village Hill Oak’ – p-cymene, terpine-4-ol, neral/citronellol

‘Sweet Mimosa’ – α-thujene, β pinene/myrcene, isomenthone

P. grossularioides – fenchone, isomenthone, citronellal, geraniol, methyl eugenol

P. filicifolium – p-cymene-8-ol

P. panduriforme – L p-cymene (37.6-45.4%)

P. hispidum – L decanoic acid (47%), 2-decanoic acid (31.3%)

Others

P. cucullatum – octyl acetate P. betulinum – L T cadinol (18.9%)

OTHER RESULTS.

N. Oyama-Okubo. 2010, Bull. Natl. Inst. Flor. Sci. 10:55-63 (In Japanese.)

Rosy Scented-

  1. Rose – β-guaiene (22.4%), β-citronellol (13.5%), citronellyl formate (11.3%)
  2. ‘Lady Plymouth’ – citronellyl formate (22.6%), β-citronellol (20.7%), β-guaiene (18%)
  3. ‘Dr. Livingston’ – β-citronellol (28.4%), iso-menthone (24.7%), citronellal (12.6%)
  4. ‘Skeleton’s Unique’ (P. radens) – β-guaiene (42.0%), β-caryophyllene (9.2%), geranyl acetate (8.5%)
  5. ‘Snowflake’ – β-guaiene (44.1%), β-citronellol (11.9%), β-caryophyllene (8.1%)

    Minty scented

  6. ‘Peppermint’ (P. tomentosum) – isomenthone (49.5%), menthone (34.0%), β-caryophyllene (7%)
  7. ‘Chocolate Peppermint’ – isomenthone (14.8%), menthone (25%), β-caryophyllene (10.3%)

    Citrusy scented-

  8. ‘Lemon’ (P. crispum) – geranial (α-citral) (38.9%), neral (β-citral) (27.2%), β-guaiene (13.5%)

    Camphor-pungent scented-

  9. ‘Clorinda’ – β-guaiene (15.7%), aromadendrene (13.2%), β-caryophyllene (9.6%)
  10. ‘Mrs. Kingsley’ – β-guaiene (41.9%), germacrene D (7.5%)
  11. ‘Sweet Mimosa’ – isomenthone (24.3%), germacrene D (9.7%)

B. Bozan et al. 1999. Pl. Med. 65:781-782 [Essential oils in flowers of P. endlicherianum] (91% of the essential oils consist of 105

compounds including the following: germacrene D (16%), β-caryophyllene (6%), α-zingiberene (3.2%), 2-phenylethyl 2 methyl

butyrate (12.5%), T-cadinol (4.7%), tricosane (5.5%). F.S. Sharopov et al. 2014 [P. graveolens grown in Tajikistan] (79 components

produce 95.1% of the essential oils including the following: citronellol (37.5%), geraniol (6%), caryophyllene oxide (3.7%),

menthone (3.1%), linalool (3%), β-bourbonene (2.7%), isomenthone (2.1%), geranyl formate (2%)).

J.A. Pino et al. 2001. [Analysis of Rose geranium oil produced in Cuba] (54 compounds produce 95.5% of the essential oil

including citronellol (25.6%), αguaiene (7.2%),caryophyllene oxide (14.7%)).

F.E. Demarne and v.d.Walt. 1992. [Essential oils of P. vitifolium with the following composition: citronellic acid (77-85%), 10-epi-gamma-eudesmol (5%)]

F.E. Demarne. 1993. [Essential oils in four natural populations of P. citronellum in South Africa with the following predominant: neral (27-37%), geranial (36-48%)]

A.M. Viljoen. 1995. [Essential oil analysis of 40 populations of P. capitatum in South Africa showed high levels of essential oil variation, consisting of 18 chemotypes.]

Characteristics of some of the primary essential oils have been described in "Why do those geraniums

smell like that?", "Why do rose geraniums smell that way?", "Trichomes" and others.

Here are ten more compounds.

Aromadendrene – sesquiterpene, with a woody fragrance, found in Eucalyptus and P. endlicherianum.

Beta guaiene – sesquiterpene, with a sweet, woody, earthy or spicy odor; found in sweet flag oil.

Germacrene D – sesquiterpene with a woody, spicy fragrance; exhibits antimicrobial and insecticidal properties;

found in feverfew, tansy and yarrow leaves and pine needles.

Linalool – terpene alcohol found in coriander, orange, lavender and basil; floral spicy fragrance; insecticide for fleas,

fruit flies, cockroaches; synthesized from geraniol, myrcene, pinene.

Myrcene – monoterpene found in thyme, cannabis, hops, lemon grass; pleasant odor (earthy to clove like to pungent

depending on concentration; from geraniol.

Octyl acetate – ester found in frankincense oil and Heracleum candolleanum rhizome, with a fruity, earthy, herbal or

waxy odor.

Piperitone – monoterpene found in Cymbopogon, Mentha (mint); peppermint, herbal, minty or camphor scent.

Spathulenol – tricyclic sesquiterpene found in Artemisia; earthy fragrance; repellant to some ants.

T-cadinol – sesquiterpenoid alcohol found in myrrh (Commiphora sp.), basil oil, pepper tree leaves, pine needles with

a balsamic or earthy fragrance; antifungal properties.

Viridiflorol – tricyclic sesquiterpene; herbal, sweet, fruity, or minty odor.

Factors affecting essential oil production – The composition of geranium oil is variable. This variability is due to the

relative concentrations of the various compounds found in the oil. In the case of commercial rose geranium oil this variation

is related to eight compounds: E and Z rose oxides, linalool, geraniol, citronellal, isomenthone, guaia-6-9-diene and

10-epi-γ-eudesmol. The composition of geranium oil is due to differences in cultivars, the climate (sunlight, rainfall,

temperature), time of harvest (the season), fertilization. Variation is also affected by soil, plant part, crop age, fertilization,

presence of weeds/disease, shade, irrigation, temperature, humidity, rainfall and time of harvest. For example, in hotter

months more citronellol is produced while in cooler months more geraniol is produced. Thus the oil produced in cooler months

would smell more citrusy, but in the warmer months the oil would smell more rosy.

Functions and effects of geranium oil – Geranium oil exhibits anti-microbial and anti-fungal properties. There are degrees

of anti-bacterial action by oils from different locations.

© 2016, Central Coast Geranium Society (CCGS )