Essential oils from leaves and bulbs of Crinum jagus (Th.) D. (Fresh and air dried): Gas Chromatography-Mass Spectrometry analysis, cytotoxic and free radical scavenging activitiesChemical composition and brine shrimp lethality of essential oils from different parts of Crinum jagus (Thompson) Dandy: Comparison between fresh and air-dried of leaves and bulbs.
A comparative study of essential oil composition, cytotoxic and antioxidant activities of fresh and air dried leaf and bulb of Crinum jagus (Th.) D were reported. Qualitative and quantitative variations in the composition of oils were investigated by GC and GC-MS. Leaf of C. jagus’s oil was characterised by high proportions of beta-ocimene (10.0-13.8%), followed by hexadecane (2.6-11.1%), tetramethylpentadecane (9.3-10.4%), phytol (7.0-9.0%), hexacosane (10.1-10.7%), nonacosane (9.7-10.3%), heptacosane (6.7-8.3%), hexahydrofarnesyl acetone (6.0-8.8%), 2,4-dimethylhexane (2.9-7.0%), and pentadecane (4.6-6.4%). Bulb oil is rich by 14-methylpentanedecanoic acid methyl ester (20.6-22.5%), teratetracontane (7.9-10.0%), hexadecanoic acid (13.6-14.1%) and 9,12-octadecadinenoic acid (14.0-14.2%).
Other constituents found in appreciable quantities included methyl benzene (5.0-6.2%), cis- decahydronaphthalene (5.8-6.5%), trans-decahydronaphthalene (4.7-5.0%), 2,4-dimethylhexane (2.9-7.0%), dodecanoic acid (3.1-3.2%) and eicosanoic acid ethyl ester (2.9-7.0%). Dried leaves and dried bulbs exhibited the highest cytotoxic activity (IC50 of 0.002 and 0.003 ?g/mL respectively) followed by fresh leaves 0.033 ?g/mL and fresh bulb 0.55 ?g/mL. The essential oils at 1.0 mg/mL displayed significant antioxidant activities. The level of antioxidant capacity varied according to samples. The chemical constituents significantly varied based on sample pre-extraction processing, thus affecting the biochemical activities.
The genus Crinum (Amaryllidacea) contains about 160 species, mainly distributed in the tropical and subtropical regions of Africa, Asia, America and Australia. Their various species attract considerable attention due to their high economical and medicinal values. Some are cultivated as ornamentals and for medical purposes. The plants from the genius are known to possess pharmacological properties, such as antitumor, antimicrobial, immunostimulating and analgesic among others. Crinum jagus (Thompson) Dandy is a perennial bulb with tulip like white flowers, which bloom during dry season on top of leafless stalks growing up to 1 m or more in height at maturity. It is locally known as ‘bush onion’ and widely used among the traditional practitioners in Africa for treatment of diabetes, obesity, diarrhea, wound, memory loss, skin sore, asthma and snake bite. Previous phytochemical investigations lead to isolation of crinamine, lycorine, psuedolycorine, hamayne and tetrahydro-1,4-oxazine. Others are calcium tetrata, 6-hydroxycrinamine and calcium oxalate. The ethanol extract of C. jagus was shown to antidiabetic, antioxidant and antimicrobial effects. Despite the great potential of Crinum species as a valuable source of bioactive compounds, no scientific data regarding the chemical composition and biological potential of essential oil from C. jagus has been reported. In view of this, the present study focused on unearthing the chemical composition, antioxidant and cytotoxic potential of essential oil from C. jagus for the first time, which is found in abundance in the South west of Nigeria.
Materials and methods
Plant material Fresh leaves and bulbs of C. Jagus were collected in November, 2013, at Ife road in Ibadan North Local Government Area of Oyo State, Nigeria. The identity of specimens was confirmed at the Department of Plant Biology, University of Ilorin, Nigeria. A voucher specimen (number UIH 1022) was deposited in the herbarium. The leaves and bulbs were air-dried without sunshine until the weight were stable and then kept for subsequent use. Fresh samples were also kept for analysis.
Chemical composition of essential oil
The yields of the essential oil obtained by hydrodistillation of the fresh leaves, dried leaves, fresh bulbs, dried bulbs of C. jagus were 0.38%, 0.21%, 0.26% and 0.40% (v/w) respectively. The chemical compositions of the extracted oils were determined using Gas Chromatography coupled to Mass Spectrometry (GC-MS) which are summarized in Table 1.A total of 57 and 56 compounds representing 99.8% and99.9% of the total oil profile were identified from the fresh and air-dried leaves respectively. In both oils, the principal constituent was beta-ocimene (10.0-13.8%), followed by hexadecane (2.6-11.1%), tetramethylpentadecane (9.3-10.4%), phytol (7.0-9.0%), hexacosane (10.1-10.7%), nonacosane (9.7-10.3%), heptacosane (6.7-8.3%), hexahydrofarnesyl acetone (6.0-8.8%), 2,4-dimethylhexane (2.9-7.0%), and pentadecane (4.6-6.4%).In the bulb, a total of 43 compounds were identified from both fresh and air-dried bulbs representing 99.8% of the total oil.
The essential oils are dominated by 14-methylpentanedecanoic acid methyl ester (20.6-22.5%), teratetracontane (7.9-10.0%), hexadecanoic acid (13.6-14.1%) and 9,12-octadecadinenoic acid (14.0-14.2%). Other constituents found in appreciable quantities included methyl benzene (5.0-6.2%), cis- decahydronaphthalene (5.8-6.5%), trans-decahydronaphthalene (4.7-5.0%), 2,4-dimethylhexane (2.9-7.0%), dodecanoic acid (3.1-3.2%) and eicosanoic acid ethyl ester (2.9-7.0%).
The volatile oils from C. jagus were analyzed with the BST to determine their cytotoxic activity. The four oil fractions evaluated were highly active with LC50 values of 0.033, 0.002, 0.55 and 0.003 ?g/mL for fresh leaf, dried leaf, fresh bulb and dried bulb respectively.
Free radical scavenging activities
The volatile oils (fresh and dried leaves; fresh and dried bulbs) of C. jagus dose dependently scavenged OH•- with the highest concentration (1000 ?g/mL) producing 91.3%, 81.6%, 70.0% and 77.1% scavenging effects at each case respectively (Figure 1). In addition, the reducing effect of the volatile oils was similar to that produced by vitamin C, and the highest activity was observed in fresh leave oil (Figure 2).
A comparative analysis of volatile chemical profiles of the leaves and bulbs C. jagus of showed significant difference in the constituents of the volatile oils (Table 1). Beta-ocimene was found to be most abundant in the oils from leaves while bulbs were characterized by a high level of 14-methylpentanedecanoic acid methyl ester. Notably the oils from the leaf lacked eicosane, similarly oils from bulb showed absence of car-2-ene, myrcene, cis-ocimene, D-limonene, allo ocimene, ?-pinene, ?-thujene, ?-terpine, ?-ocimene, fenchone, neral, and geranial which were all monoterpenes hydrocarbons. Other notewhorthy oxygenated monoterpenes compounds absent were geraniol, nerol and borneol. They contained more (majorly) sequiterpenes hydrocarbons and other higher hydrocarbons than the leaves oil. The content of their higher hydrocarbons (viz: 14-methylpentanedecanoic acid methyl ester, teratetracontane, hexadecanoic acid and 9,12-octadecadinenoic acid) seen in the air dried bulb’s oil is similar to that previously reported for a sample derived from dried bulb of C. ornatum (Ait.) Bury. For the bulb, FB and DB also produced volatile oils with similar chemical constituents.
The oils were characterized by a low content of mono- and sesquiterpenoid, but high content of aliphatic hydrocarbons. In addition, chemical profiles of fresh and air dried volatile oils of the bulbs are the same, though quantitative differences can be seen for some individual compounds. For the leaf, fresh and air-dried gave essential oils containing identical constituents with exception of methyl benzene in air-dried, but the quantitative composition differed significantly. Drastical reduction in the amounts of benzyl alcohol, car-2-ene, myrcene, cis-ocimene, D-limonene, allo ocime, alpha-pinene, alpha-thujene, gamma-terpine was observed on drying the leaves and similar trends were noticed for fenchone, neral, geranial, isoartemisia, 1,8-cineole, geraniol, nerol, borneol, eugenol, linalool, ?-terpinol, terpinen-4-ol and ?-caryophyllene. Other constituents with significant reduction in quantity were thymyl methyl ether, linalyl acetate, ethyl cinnamate, ?-cadinene, ?-elemene, ?-pinene, ?-cadinene, hexadecane, ?-muurolene and trans-decahydronaphthalene. However, percentage composition of ?-ocimene, 2,4-dimethylhexane and bisabolene increased (about 30%) drastically after air drying; similar increments (> 30%) were recorded for hexahydrofarnesyl acetone, tetracosane, heptacosane, nonacosane and phytol.Generally, analysis of the four oils showed that they were predominantly monoterpene, oxygenated monoterpene, sesquiterpene and other higher hydrocarbons.
Although, the latter group of compounds were quantitatively the major constituents. There are forty one compounds which are common in both leaf and bulb oils. The leaf oils were characterized by the abundance of ?-ocimene which is not detected in bulb oils. Methyl benzene, cis-decahydronaphthalene and other major compounds in the bulbs oils are detected in very low amount in the leaf oil. Similarly, C-20 hydrocarbon eicosane, abundant in bulb oils is absent in leaf oils. The chemical constituents seen in the oil of this specimen (air-dried bulb) was similar to that previously reported for a sample (air dried bulb) from Crinum ornathum (Ait.) Bury, a different species (Oloyede et al. 2010). The oil described here however, differed with the presence of mono- and sesqui-terpenes hydrocarbons. The observed variations or similarities are often ascribed to the existence of specific chemotypes, which would be interesting for further study. In addition, chemical profiles of fresh and air dried volatile oils of the bulbs are the same, though quantitative differences can be seen for some individual compounds. ?-caryophelle (1.8-2.7%) and 2,4-dimethylhexane (3.9-7.0%) were common constituents of the studied oils which occurred in appreciable quantity. A significant correlation between brine shrimp toxicity and 9KB (human epidermoid carcinoma of nasopharynx) cytotoxicity (p = 0.036 and kappa = 0.56) has been established; and many novel antitumor and pesticidal natural products have been discovered using this bioassay (BST).