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Siddiqui et al. Chem Synth 2023;3:25 https://dx.doi.org/10.20517/cs.2023.02 Page 7 of 50

Figure 6. Biotransformation of thymoquinone (31) with Aspergillus niger.

Figure 7. Microbial transformation of (+)-isolongifolen-4-one (35) with Aspergillus niger and Fusarium lini.

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metabolite 43 decreased its activity (IC = 299.5 μM) [Figure 8].
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Biotransformation of 5α-hydroxycaryophylla-4(12), 8(13)-diene (45)
Macrophomina phaseolina-mediated structural transformation of the naturally occurring sesquiterpene, 5α-
hydroxycaryophylla-4(12), 8(13)-diene (45) resulted in three new metabolites, 4β-methoxycaryophyllene-5α,
14-diol (46) (3.5%), 4β-methoxycaryophyllene-5α, 15-diol (47) (7.6%), and caryophyllene-5α, 15-diol (48)
(2.7%) [Figure 9]. The transformed products 46 (IC = 3.09 ± 2.61 μg/mL), 47 (IC = 0.72 ± 0.17 μg/mL),
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50
and 48 (IC = 1.35 ± 0.43 μg/mL) showed significant anti-malarial activity, in comparison to the standard,
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chloroquine diphosphate (IC = 0.025 ± 0.01 μg/mL) by using parasite lactate dehydrogenase assay
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in vitro .
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Biotransformation of (-)-caryophyllene oxide (49)
Biotransformation of another sesquiterpene (-)-caryophyllene oxide (49), a common constituent of essential
oils, with the cell suspension culture of medicinal plant Catharanthus roseus afforded two new derivatives, 2
β-hydroxycaryophyllene oxide (50) (7.5%), and 2-hydroxy-4, 5- epoxycaryophyllan-13-ol (51) (4.6%), along
with two known derivatives, 15-hydroxycaryophyllene oxide (52) (2%), and 4β, 5α-dihydroxycaryophyll-8 (
13) -ene (53) (6%) [Figure 10].
[30]

In addition, biotransformation of (-)-caryophyllene oxide (49) with the fungal cell culture Cephalosporium
aphidicola yielded two known metabolites, 4β, 5α-dihydroxycaryophyll-8 (13) -ene (53) (2.7%) and clovane-
5,9-diol (54) (1.3%) [Figure 11] [Proposed Supplementary Figure 3]. Similarly, fungal transformation of 49
with Macrophomina phaseolina also yielded two known transformed products, 15-hydroxycaryophyllene