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Two new lignans, namely 7-O-podophyllotoxinyl butyrate (1) and dihydroclusin 9-acetate (2), were isolated from the dichloromethane fraction of a methanol extract of Bursera microphylla (Burseraceae), along with eight known lignans (3-10). Their structures were determined by means of comprehensive spectroscopic analysis. Lignans 2-6 were tested for their anti-proliferative activity on the cancer cell lines LS180, A549 and HeLa, and on a non-cancer cell line, ARPE-19. Only compounds 4 and 5 showed an interesting activity on HeLa cells.

The genus Bursera belongs to the family Burseraceae and has been used in traditional Mexican medicine for treating various pathophysiological disorders. The most representative phytochemicals isolated from this genus are terpenoids and lignans. Lignans are phenolic metabolites known for their antioxidant, apoptotic, anti-cancer, anti-inflammatory, anti-bacterial, anti-viral, anti-fungal, and anti-protozoal properties. Though the genus includes more than 100 species, we have attempted to summarize the biological activities of the 34 lignans isolated from selected Mexican Bursera plants.

Bursera microphylla (BM), one of the common elephant trees, is widely distributed in the Sonoran Desert in Mexico. The Seri ethnic group in the Sonoran Desert uses BM as an anti-inflammatory and painkiller drug for the treatment of sore throat, herpes labialis, abscessed tooth, and wound healing. Dried stems and leaves of BM are used in a tea to relieve painful urination and to stimulate bronchial secretion. Furthermore, BM is used for fighting venereal diseases. To investigate the effects of the hexane fraction of resin methanol extract (BM-H) on cell growth, the acute myeloid cell line (OCI-AML3) was treated with 250, 25, or 2.5 µg/mL of BM-H. The first 2 concentrations were able to significantly decrease OCI-AML3 cell number. This reduced cell number was associated with decreased S-phase, blockade of the G 2 /M phase of the cell cycle, and increased cell death. Similar results were obtained on all tested tumor cell lines of different origins. We found that blockade of the cell cycle was due to upregulation of p21 protein in a p53-independent way. Increase of p21 was possibly due to upstream upregulation of p-ERK (which stabilizes p21 protein) and downregulation of p-38 (which promotes its degradation). Regarding cell death, activation of caspase-3, but not of caspase-8 or -9, was detectable after BM-H treatment. In conclusion, these data suggest that the BM's hexane fraction inhibited proliferation of cell lines mainly by a p21-dependent, p53-independent mechanism and promoted apoptosis through activation of caspase-3, but not caspase-8 or -9.

Bursera microphylla (BM), one of the common elephant trees, is widely distributed in the Sonoran desert in Mexico. The Seri ethnic group in the Sonoran desert uses BM as an anti-inflammatory and painkiller drug for the treatment of sore throat, herpes labialis, abscessed tooth, and wound healing. Dried stems and leaves of BM are used in a tea to relieve painful urination and to stimulate bronchial secretion. Furthermore, BM is used for fighting venereal diseases. To investigate the effects of the hexane fraction of resin methanol extract (BM-H) on cell growth, the acute myeloid cell line (OCI-AML3) was treated with 250, 25, or 2.5 µg/mL of BM-H. The first 2 concentrations were able to significantly decrease OCI-AML3 cell number. This reduced cell number was associated with decreased S-phase, blockade of G 2 /M phase of the cell cycle, and increased cell death. Similar results were obtained on all tested tumor cell lines of different origins. We found that blockade of the cell cycle was a result of upregulation of p21 protein in a p53-independent way. Increase of p21 was possibly a result of upstream upregulation of p-ERK (which stabilizes p21 protein) and downregulation of p-38 (which promotes its degradation). Regarding cell death, activation of caspase-3, but not of caspase-8 or -9, was detectable after BM-H treatment. In conclusion, these data suggest that BM-H inhibited proliferation of cell lines mainly by a p21-dependent, p53-independent mechanism and promoted apoptosis through activation of caspase-3 but not caspase-8 or -9.

Copal is the Spanish word used to describe aromatic resins from several genera of plants. Mexican copal derives from several Bursera spp., Protium copal, some Pinus spp. (e.g., P. pseudostrobus) and a few Fabaceae spp. It has been used for centuries as incense for religious ceremonies, as a food preservative, and as a treatment for several illnesses. The aim of this review is to analyze the chemical composition and biological activity of commercial Mexican Bursera copal.

A chemical study of the nonpolar fraction of a methanol-soluble extract of Bursera microphylla resin yielded a variety of di- and triterpenoids. In total, 15 compounds were isolated, of which three are new, namely, malabaricatrienone (1), malabaricatrienol (2), and microphyllanin (3). The antiproliferative activity of the major compounds was evaluated in different murine cancer cell lines (M12.C3.F6 and RAW264.7) and human cancer cells (A549, HeLa, and PC-3). The new compounds (1-3) did not show significant antiproliferative activity. The known compounds ariensin (4), burseran (5), and dihydroclusin diacetate (6) were effective against the RAW264.7 cell line, with IC50 values in the micromolar range.