Chemical composition of the essential oil and botanical study of the flowers of Mentha suaveolens

Figures & data

Table 1. Chemical composition of the essential oil of flowers of M. suaveolens Ehrh. cultivated in Egypt.

Peak	Kovat's index	Identified component	Percentage
1	1021	Limonene	31.25
2	1035	γ-Terpinene	0.01
3	1088	Linalool	0.32
4	1150	Borneol	0.68
5	1168	cis-Dihydrocarvone	0.15
6	1175	trans-Dihydrocarvone	0.85
7	1193	cis-Carveol	2.31
8	1235	Carvone	50.59
9	1296	Dihydrocarveol acetate	0.36
10	1305	trans-Carvyl acetate	0.35
11	1324	Piperitenone	0.12
12	1333	cis-Carvyl acetate	0.44
13	1357	β-Bourbonene	1.27
14	1380	cis-Jasmone	1.27
15	1397	trans-β-Caryophellene	2.56
16	1407	β-Cedrene	0.32
17	1423	β-Copaene	0.28
18	1435	α-Humulene	1.24
19	1447	γ-Muurolene	0.61
20	1465	Germacrene d	2.04
21	1483	Bicyclogemacrene	0.35
22	1502	γ-Cadinene	0.13
23	1511	trans-Calamenene	0.45
24	1527	α-Cadinene	0.09
25	1577	Caryophyllene oxide	0.30
26	1603	Cubenol-1,10-di-epi	0.31
27	1627	epi-α-Cadinol	0.50
28	1640	epi-α-Muurolol	0.34
29	1965	Manoyl oxide	0.28
Number of identified compounds			29
% of identified components			99.77
Classes of the essential oil components
A-Hydrocarbons			40.60
• Monoterpenes			31.26
• Sesquiterpenes			8.89
• Aromatic hydrocarbons			0.45
B-Oxygenated constituents			59.17
• Monoterpenes			56.17
• Sesquiterpenes			1.45
• Other oxygenated constituents			1.55

Figure 1. Photographs of Mentha suaveolens Ehrh. (A) A flowering branch of Mentha suaveolens Ehrh. (X = 0.6). (B) The inflorescence (X = 1). (C) The bract (X = 10). (D) The flower (X = 12).

Figure 2. Transverse section of the rachis of the inflorescence of Mentha suaveolens Ehrh. (A) Low power view (X = 30). (B) High power view (X = 215). (C) High power view from the corners (X = 315). col., collenchyma; c.par., cortical parenchyma; end., endodermis; ep., epidermis; m.r., medullary ray; n.gl.t., non-glandular trichomes; per., pericycle; ph., phloem; pi., pith; xy., xylem.

Figure 3. Transverse section of the bract of Mentha suaveolens Ehrh. (A) Low power view (X = 40). (B) High power view of the midrib (X = 100). (C) High power view of the lamina (X = 333). c.par., cortical parenchyma; ca., cambium; gl.t., glandular trichomes; l.ep., lower epidermis; m.r., medullary ray; n.gl.t., non-glandular trichomes; pal.t., palisade tissue; per., pericycle; ph., phloem; sp.t., spongy tissue; u.ep., upper epidermis; xy., xylem.

Figure 4. Epidermal cells of the rachis and bract of Mentha suaveolens Ehrh. (A) Epidermal cells of the rachis (X = 450). (B) Upper epidermal cells of the bract (X = 433). (C) Lower epidermal cells of the bract (X = 433). cap.gl.t., capitate glandular trichomes; cic., cicatrix; lab.gl.t., labiaceous glandular trichomes; str.cu., striated cuticle.

Figure 5. Transverse section of the flower of Mentha suaveolens Ehrh. (At the upper part of the calyx) (X = 60). ant., anther; pet., petals; p.gr., pollen grains; sep., sepals; sty., style.

Figure 6. Micromorphology of the calyx and corolla of Mentha suaveolens Ehrh. (A) Transverse section of the sepal (X = 60). (B) Inner epidermal cells of the calyx at the base (X = 450). (C) Inner epidermal cells of the calyx at the tip (X = 450). (D) Outer epidermal cells of the calyx at the base (X = 450). (E) Outer epidermal cells of the calyx at the tip (X = 450). (F) Transverse section of the petal (X = 140). (G) Inner epidermal cells of the corolla at the base (X = 775). (H) Inner epidermal cells of the corolla at the tip (X = 775). (I) Outer epidermal cells of the corolla at the base (X = 775). (J) Outer epidermal cells of the corolla at the tip (X = 775). c.par., cortical parenchyma; l.ep., lower epidermis; n.gl.t., non-glandular trichomes; u.ep., upper epidermis; v.b., vascular bundle.

Figure 7. Micromorphology of the androecium and gynaecium of Mentha suaveolens Ehrh. (A) Detailed transverse section of the anther (X = 160). (B) Detailed transverse section of the filament (X = 125). (C) Detailed transverse section of the ovary (X = 160). (D) Ovary wall (X = 333). (E) Transverse section of the style (X = 267). (F) Transverse section of the stigma (X = 217). c.par., cortical parenchyma; c.t., connective tissue; ep., epidermis; f.l., fibrous layer of anther; i.ep., inner epidermis; n.gl.t., non-glandular trichome; o.ep., outer epidermis; ov., ovule; o.w., ovary wall; p.gr., pollen grains; p.s., pollen sac; v.b., vascular bundle.

Figure 8. Powdered inflorescence of Mentha suaveolens Ehrh. ep.an, epidermis of anther (X = 650); ep.br, epidermis of bract (X = 433); ep.ca, epidermis of calyx (X = 450); ep.cr, epidermis of corolla (X = 775); ep.fil, epidermis of filament (X = 650); ep.ov., epidermal cells of the ovary (X = 375); ep.ra, epidermis of rachis (X = 450); ep.stg., epidermal cells of the stigma (X = 450); ep.sty., epidermal cells of the style (X = 525); f.l., fibrous layer of anther (X = 650); gl.t., glandular trichomes (X = 433); m.r., medullary ray (X = 550); n.gl.t., non-glandular trichomes (X = 433); p.gr., pollen grains (X = 650); pal., palisade cells (X = 400); v.o.dp., volatile oil droplets (X = 300); w.f., wood fibers (X = 233); w.p., wood parenchyma (X = 500); x.v., xylem vessel (X = 750).

Table 2. Microscopical measurements of the different organs of the inflorescence M. suaveolens Ehrh.

Element	Length	Height	Width	Diameter
1. The rachis
Epidermal cells	17–33–45	15–26–33	2–4–6	–
Glandular trichomes
Capitate type
• The stalk	4–9–11	8–11–13	–	–
• The head	20–22–25	16–20–22	–	–
Labiaceous type
• The head	–	–	–	35–37–40
Non-glandular trichomes	100–105–111	6–8–12	–	–
Medullary rays	11–23–27	14–16–18	–	–
Wood fibres	278–280–386	8–9–13	–	–
Wood parenchyma	55–62–67	31–33–37	–	–
Xylem vessels	–	–	–	17–20–23
Volatile oil droplets	–	–	–	4–5–8
2. The bract
Upper epidermal cells	22–31–34	13–22–25	35–40–42	–
Lower epidermal cells	26–33–48	11–17–34	25–32–40	–
Upper neural cells	15–26–40	6–13–23	–	–
Lower neural cells	13–22–41	8–13–23	–	–
Glandular trichomes
Capitate type
• The stalk	11–18–46	11–18–27	–	–
• The head	15–23–34	15–23–29	–	–
Labiaceous type
• The head	–	–	–	40–43–49
Non-glandular trichomes	115–138–162	4–6–9	–	–
Xylem vessels	–	–	–	21–25–28
Palisade cells	12–17–28	5–7–10	–	–
Volatile oil droplets	–	–	–	3–4–5
3. The flower
(a) The calyx
Inner epidermis at the base	13–22–33	6–8–12	–	–
Inner epidermis at the tip	15–22–35	13–18–31	–	–
Outer epidermis at the base	15–20–37	6–13–15	–	–
Outer epidermis at the tip	9–11–33	6–11–13	–	–
Stomata	17–19–23	13–15–18	–	–
Glandular trichomes
Capitate type
• The stalk	3–5–11	3–4–7	–	–
• The head	11–13–20	10–13–15	–	–
Labiaceous type
• The head	–	–	–	41–44–45
Non-glandular trichomes	24–33–46	6–9–23	–	–
Xylem vessels	–	–	–	15–18–20
Volatile oil droplets	–	–	–	3–4–5
(b) The corolla
Inner epidermis at the base	19–21–32	11–13–15	–	–
Inner epidermis at the tip	15–16–33	10–13–23	–	–
Outer epidermis at the base	21–23–38	3–5–7	–	–
Outer epidermis at the tip	6–13–20	3–5–7	–	–
Glandular trichomes
Capitate type
• The stalk	9–13–15	7–8–10	–	–
• The head	19–20–23	13–16–18	–	–
Labiaceous type
• The head	–	–	–	30–31–34
Non-glandular trichomes	57–69–80	18–23–30	–	–
(c) The androecium
Epidermis of filament	17–23–48	11–14–18	9–15–21	–
Epidermis of anther	6–10–22	3–5–9	8–9–11	–
Fibrous layer of anther	14–15–20	5–7–10	–	–
Pollen grains	–	–	–	7–11–15
(d) The gynaecium
Epidermis of ovary	18–20–35	12–15–20	–	–
Epidermis of style	8–11–30	7–8–12	7–11–13	–
Epidermis of stigma	2–10–18	1–3–6	9–13–16
Non-glandular trichomes	44–46–48	8–10–13	–	–

The underlined numbers indicate average values.