Background: The current study was undertaken to assess the cytotoxicity of the leaves of Libyan Juniperus phoenicea (Cupressaceae) against human cancer cell lines. Methods: The cytotoxicity of the n-hexane, dichloromethane (DCM) and methanol (MeOH) extracts of the leaves of J. phoenicea (JP), obtained from sequential Soxhlet extractions, was assessed against four human cancer cell lines: EJ138 (human bladder carcinoma), HepG2 (human liver hepatocellular carcinoma), A549 (human lung carcinoma) and MCF7 (human breast adenocarcinoma) using the MTT assay. Results: The cell line A549 was the most sensitive to the JP extracts, with the highest level of cytotoxicity with the IC50 values of 16, 13 and 100 µg/mL for the DCM, n-hexane and MeOH extracts, respectively. However, generally the most potent cytotoxic extract across the other cells tested was the n-hexane extract, followed by the DCM extract, whilst the MeOH extracts showed little or no cytotoxicity. The percentage of viability of cells decreased as the concentration of test compounds increased. The cytotoxicity of various chromatographic fractions from the extracts was also studied against the A459 cells. For the n-hexane fractions, the IC50 values were 160, 62, 90, 30, 9.5 and 40 µg/mL for fractions 1 to 5 and 7, respectively. Fractions 4 and 5 showed the greatest effect. DCM fractions 2, 3 and 4 had the IC50 values of 60, 92 and 19 µg/mL, respectively, and DCM fractions 5 to 8 were non-cytotoxic. Fractions 1 and 2 of the MeOH extract were non-cytotoxic, whereas cytotoxicity was observed for fractions 3 and 4 with IC50 values of 50 and 85 µg/mL, respectively. Conclusion: The outcome of the present study suggested that the JP leaves possess cytotoxic activities. The high level of cytotoxicity of the n-hexane and DCM extracts suggested that lipophilicity might affect the cytotoxicity of JP, where the less polar compounds had the strongest cytotoxicity.

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Three biflavonoids [cupressuflavone (1), amentoflavone (2), and sumaflavone (3)], four diterpenoids [13-epi-cupressic acid (4), imbricatholic acid (5), 3-hydroxysandaracopimaric acid (6), and dehydroabietic acid (7)], and one lignan [β-peltatin methyl ether (8)] were isolated from the cytotoxic fractions of the extracts of the leaves of the Libyan Juniperus phoenicea L. The structures of these compounds were elucidated by spectroscopic means. Cytotoxicity of compounds 1-6 were assessed against the human lung cancer cell line A549 using the MTT assay. Compounds 1 and 3 showed cytotoxicity against the A549 cells (IC 50 = 65 and 77 μM, respectively), whereas compound 2 did not show any activity. Diterpenes 4-6 exhibited weak cytotoxicity against the A549 cells with the IC 50 values of 159, 263, and 223 μM, respectively. The cytotoxicity of each compound was compared with the anticancer drug, etoposide (IC 50 = 61 μM). Cupressuflavone (1) was evaluated also for cytotoxicity against both the human PC3 cancer cell line and the normal prostate cell line (PNT2), and this compound revealed a high degree of cytotoxic selectivity towards the prostate cancer cells (PC3), with IC 50 value of 19.9 μM, without any evidence of cytotoxicity towards the normal prostate cell line (PNT2).

Arbutus pavarii Pamp. (Fam. Ericaceae), an endemic Libyan medicinal plant, is commonly known as “Shmeri”, “Shmar” or “Libyan Strawberry”, and almost exclusively found in the Al-Jabel Al-Akhdar mountainous region in Libya. This plant is a forage species for honeybees and thus, is important for honey production. A. pavarii has long been used in Libyan traditional medicine to treat both gastritis and kidney diseases. Previous limited phytochemical studies on this plant furnished the presence of simple phenolics like arbutin and gallic acid, and polyphenolics including flavonoids and tannins, for example, apigenin, epicatechin, hesperidin, kaempferol, naringin, quercetin and rutin, as well as some triterpenes and sterols. This paper describes, for the very first time, a cytotoxicity assay-guided isolation of the major active compound from the methanol extract of the leaves of A. pavarii, and its identification as ursolic acid (1) by comprehensive spectroscopic analyses. Dhaka Univ. J. Pharm. Sci. 20(3): 267-274, 2022 (June) Centennial Special Issue

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