Phytochemical Analysis and Biological potential of leaves and peels of three Eastern Cape Citrus Species

Citrus sinensis, Citrus reticulata and Citrus clementine are citrus species that belong to a large family Rutaceae. Citrus leaves and peels are often regarded as waste products. In view of the environment pollution impact, the search for end use of citrus waste products for economic value and medicinal purposes was sort after. The aim of this study was to investigate chemical composition of citrus waste products (leaves and peels) essential oils and determine biological active volatile compounds from Citrus sinensis, Citrus reticulata and Citrus clementine Leaves and peels of Citrus sinensis, Citrus reticulata and Citrus clementine collected twice from citrus farm were extracted for essential oils using hydrodistillation method and analysed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) for plant samples collected in 2016 and, gas chromatography (GC) and gas chromatography-triple quadrupole-mass spectrometry (GC-MSMS) for plant samples collected in 2017. The oil yield for Citrus sinensis was 0.19 - 0.85 %v/w for fresh and dried leaf and peels for samples collected in 2016 and 0.26 – 0.87% v/w for those collected in 2017. Analysis of the essential oils analyses identified sabinene (20.4% GCMS, 22.6% GCMSMS), terpinen-4-ol (13.2% GCMS, 6.8% GCMSMS) and linalool (7.6% GCMS, 19.3% GCMSMS) as major compounds in fresh leaves essential oils while β-elemene (16.3% GCMS, 21.4% GCMSMS) and sabinene (10.7% GCMS, 20.8% GCMSMS) were major compounds characterized in dried leaves essential oils. Fresh and dried peels essential oils had limonene as the major constituent (49.6% GCMS, 87.1% GCMSMS) and (73.6% GCMS, 88.3% GCMSMS) respectively. Citrus reticulata essential oils percentage yield range between 0.44-0.80% v/w for fresh and dried leaf and peel oils. Analyses of the GCMS and GCMSMS chromatogram of the volatile oils analyses revealed linalool (33.4% GCMS, 19.6% GCMSMS), (+)-spathulenol (15.2% GCMS, 10.1% GCMSMS) and terpinene-4-ol (4.5% GCMS, 11.9% GCMSMS) as major compounds in fresh leaf essential oils while, sabinene (20.8% GCMS, 32.5% GCMSMS) and linalool (17.2% GCMS, 20.4% GCMSMS) were the major compounds found in dried leaf essential oils. Limonene (55.2%, 75.4% GCMS; 39.5%, 80.8% GCMSMS) was the major prominent compound identified in the C. reticulata peel essential oils in fresh and dried peels respectively, followed by linalool (12.8%, 2.9% GCMS; 48.4%, 7.4% GCMSMS). Percentage yields for the essential oils from C. clementine fresh and dried leaves and peels ranges from 0.40-0.62% v/w for. Fresh and dried leaves volatile oils had sabinene (22.7-27.1%) for GCMS and GCMSMS respectively), linalool (18.5- 20.9% GCMS and GCMSMS) and terpinene-4-ol (6.5- 11.8% GCMS and GCMSMS) as main compounds while fresh and dried peels oils were dominated by limonene (38.9- 86.5% GCMS and GCMSMS). Phytochemical screening experiment of the three citrus species leaves and peels aqueous extract reveal the prominent presence of flavonoids and phenolic compounds in high concentrations. C. reticulata and C. clementine peels and leaves volatile oils exhibited higher antioxidant activity as DPPH free radical scavengers and Ferric reducing power (FRAP) ability, when compared to C. sinensis essential oils which exhibited minimum antioxidant activity. Antioxidant activity of leaves and peels essential oils maybe due to the presence of oxygenated monoterpenes and high limonene content. C. sinensis peels oils showed non-toxic to extremely very low toxicity effect at highest dose 2000 mg/kg. C. reticulata and C. clementine peels oils showed toxicity effect in mice at high dose levels. It is suggested that citrus volatile oils could be safe to use at lower dose levels. Citrus species peels and leaves volatile compounds limonene linalool and sabinene exhibited antiinflammatory activity by significantly reducing rats paw oedema size induced by fresh egg albumin. The study suggests the use of Citrus waste products (leaves and peels) as natural antioxidants with antiinflammatory properties for medicinal value and volatile oils compounds for aroma in beverages and cosmetic industries