Composición química y actividad antioxidante de aceites esenciales de Tanacetum vulgare y Mentha x piperita L. var. vulgaris cultivados en Cusco, Perú

Tanacetum vulgare L. (Asteraceae), known as “tansy” in Europe and “Palma real” in Peru, is an aromatic plant widely used in folk medicine as a vermifuge and anti-inflammatory.^1,2 Also, the aerial parts of this plant are popularly used to treat migraine, neuralgia, and rheumatism, and as an anthelmintic and insect repellent.³ Tansy extract has been reported to exhibit antitumor,⁴ anti-inflammatory,⁵ antioxidant,⁶ and antimicrobial activity.⁷ Papers on the composition of the oils of this species published up to 1996 have been reviewed.⁸ Twenty-three chemotypes of the oils of tansy plants have been determined according to the most dominant constituent in the essential oils.⁸ The most common, a β-thujone chemotype was identified in nine countries: Argentina, Belgium, Canada, Holland, Poland, Hungary, Finland, India and Italy, while an α-thujone chemotype occurred in three countries: France, Germany and Italy. Camphor type oils were collected in plants from seven countries (Belgium, Germany, Holland, Hungary, Finland, Kazakhstan and USA) and of trans-chrysanthenyl acetate chemotype – in five ones (Belgium, Finland, Holland, Hungary and Italy). The 1,8-cineole and artemisia ketone chemotypes were present in Holland, Hungary and Finland. Other 16 chemotypes in which the dominant constituent is one of the following α-pinene, sabinene, g- terpinene, thujyl alcohol, thujyl acetate, umbellulone, chrysanthenone, chrysanthenone oxide, isopinocamphone, borneol, piperitone, trans-dihydrocarvone, lyratol, lyratyl acetate, davanone or germacrene D occurred in few countries.⁸ Papers on the composition of tansy oils published later,^9-13 only found one new chemotype in which dominant components were β-thujone-trans-chrysanthenyl acetate.¹⁴,¹⁵

The well-known and widely used peppermint (Mentha . piperita L.) (Lamiaceae) is a cultivated natural hybrid of Mentha aquatica L. (water mint) and Mentha spicata L. (spearmint). Although is native to the Mediterranean region, it is cultivated all over the world for its fragrant oil. Peppermint essential oil is used in flavor, fragrance, medicinal, and pharmaceutical applications.^16-19 More than 300 constituents have been identified in the essential oil, where the major constituents are menthol (35-60 %), menthone (2-44 %), menthyl acetate (0.7-23 %), 1,8-cineole (1-13 %), menthofuran (0.3-14 %), isomenthone (2-5 %), neomenthol (3-4 %) and limonene (0.1-6 %).^20,21

Despite the medicinal potential of plants in Peru being considerable, knowledge of this area and studies on the biological activities of these plants remained scarce. Furthermore, as far as our literature survey could as certain, antioxidant activities of the Peruvian aromatic plants Tanacetum vulgare L. and Mentha . piperita L. var. vulgaris have not previously been published, although, there are many reports concerning essential oils from these species in other countries. Moreover, knowing that the chemical composition and activity of essential oils from aromatic plants depends on several factors such as the geographical origin, the aims of this study were (i) to determine the composition of the essential oils isolated from the leaves of Tanacetum vulgare L. and Mentha . piperita L. var. vulgarisgrown wild at high height above sea level and (ii) to assess the antioxidant activities of these essential oils.

The extraction yield of T. vulgare and M. . piperita var. vulgaris essential oils were 0.4 % and 0.8 % (v/m), respectively.

Quantitative data expressed as average percentage values and standard deviations, of single components in the essential oils are listed in Table 1. Fifty components were identified in the essential oil from T. vulgare leaves. As can be seen, oxygenated monoterpenes were the most represented class of volatile with 92.6 %. Amongst their derivative, trans-thujone or β-thujone was the major compound. This chemical composition suggests that the analyzed tansy plant belong to the most common trans-thujone chemotype. This monoterpenic ketone is a bioactive compound with medicinal properties, but at high concentrations it exhibits toxicity.^25-28

Seventy constituents were identified in the essential oil from Mentha . piperita leaves (Table 1). The essential oil contains basically oxygenated monoterpenes (67.7 %) being the major constituents menthol, menthyl acetate, and menthone. Menthofurane was not detected in the present study, but developmental and environmental factors are known to influence greatly the yield and composition of peppermint essential oils.¹⁸ The composition found in the present study is according to the general criteria that high quality peppermint essential oils have higher quantities of menthol and menthone, and lower amounts of pulegone and menthofuran.¹⁸

DPPH is a free radical compound which is usually used as in vitro test to evaluate the ability of the several compounds to free radical scavenging. At this work, the antioxidant effect of the essential oils from T. vulgare and M. x piperita var. vulgaris was tested by using this assay.

Tansy antioxidants have been studied rather scarcely and mainly as extracts.^6,29,30 The essential oils from T. vulgare had the capacity to scavenge the DPPH radical, showing a maximal effect of 58.26 ± 0.9 % at the concentration of the 4 500 μg/mL. On the other way, usually DPPH scavenging is presented by the IC50 value, concentration of antioxidant needed to scavenged 50 % of the DPPH radical present into the test solution. For this tansy essential oil the IC50 value was 3 525 ± 123 μg/mL. But, as can be seen, this effect was very lower than the observed for M. x piperita var. vulgaris essential oil and the ascorbic acid, the positive control used in the assay, which showed a percentage of inhibition of 89.0 ± 4.3 % at 100 μg/mL (Table 2).

Table 2
Scavenging effect of Tanacetum vulgare and Mentha x piperita var vulgare essential oils on DPPH radical

Antioxidant effectiveness expressed as IC50, the total antioxidant capacity necessary to decrease the initial DPPH radical concentration by 50 %. Values represent average of three determinations with ± standard deviation. Ascorbic acid was used as standard.

In addition, M. x piperita var. vulgaris essential oil exhibited concentration dependent increase to DPPH radical scavenging effect, the maximum effect observed was 69.1 ± 3.4 % at 500 μg/mL. On the other hand, the IC50 value for this tested product was 136.4 ± 35 μg/mL. Studies performed for evaluating the free radical scavenging capacity of essential oils from other species of Mentha showed the antioxidant properties of this species, where one variety of M. x piperita var. vulgaris expressed IC50 values of 2.53 µg/mL.³¹ At this study the most powerful scavenging compounds associated to antioxidant activity of M. x piperita were monoterpene ketones, particularly the menthone and iso-menthone. Comparison of the DPPH scavenging property from oils present in the M. x piperita var. vulgaris evaluated by us and previously reported31 for M. x piperita and the found for ascorbic acid (51.2 ± 2.9 μg/mL at 100 μg/mL) in our study, the essential oil evaluated at the present study exhibited weakest antioxidant effects than the previously report for the specie and the standard antioxidant.

The essential oil from Tanacetum vulgare has lower antioxidant activity than Mentha . piperita var. vulgaris, but both have potential use in food industry, cosmetic or pharmaceutical industries.

Table 1
Composition of the essential oils of Tanacetum vulgare and Mentha x piperita var. vulgaris leaves.

a RIA and RIP, experimental linear retention indices on DB-5ms and DB-Wax column, respectively.b RIAO and RIPO, linear retention indices from standard or literature on DB-5ms and DB-Wax column, respectively. ctrace (<0.1%).* tentatively identified compound by comparison with literature data.