Essential Oil Composition and In Vitro Biological Activities of Seven Namibian Species of Eriocephalus L. (Asteraceae)

Abstract

The essential oil composition of seven Namibian Eriocephalus species (E. dinteri, E. ericoides subsp. ericoides, E. klinghardtensis, E. luederitzianus, E. merxmuelleri, E. pinnatus, E. scariosus) were determined by GC and GC/MS. The oils of E. ericoides subsp. ericoides (sample 1), E. merxmuelleri and E. scariosus were found to be rich in 1,8-cineole and camphor. Eriocephalus scariosus oil contained santolina alcohol (14.8%). The highest levels of camphor (38.4%) was found in E. dinteri oil. The major component of E. ericoides subsp. ericoides (sample 2) was linalool (10.4%). A chemical similarity between E. luederitzianus and E. klinghardtensis was observed which both accumulated high levels of α-pinene, β-pinene, p-cymene and γ-terpinene. Eriocephalus luederitzianus oil contained α-longipinene (10.3%) and β-caryophyllene (13.3%). The morphologically anomalous E. pinnatus was very different in oil composition when compared to the other taxa and is characterized by isoamyl 2-methylbutyrate (7.9%) and isoamyl valerate (6.5%). Antimicrobial disc diffusion assays and minimum inhibitory concentrations (MIC) were performed on all seven species. Good antifungal activity was noted for E. ericoides subsp. ericoides. Highest activities were noted for E. merxmuelleri against the Gram-positive test organisms and generally poor activity was noted against the Gram-negative test organisms for all species. The anti-inflammatory activity of the oils were assessed using the 5-lipoxygenase (5-LOX) enzyme and E. dinteri displayed the most promising inhibition (IC₅₀ = 35 μg/ml).

Key Word Index:

• Eriocephalus dinteri
• Eriocephalus ericoides subsp. ericoides
• Eriocephalus klinghardtensis
• Eriocephalus luederitzianus
• Eriocephalus merxmuelleri
• Eriocephalus pinnatus
• Eriocephalus scariosus
• Asteraceae
• Namibia
• essential oil composition
• chemotaxonomy
• α-pinene
• β-pinene
• 1,8-cineole
• santolina alcohol
• linalool
• chrysanthenone
• camphor
• α-longipinene
• β-caryophyllene
• antimicrobial activity
• anti-inflammatory activity