Phenolic compounds content, antioxidant and antimicrobial activities of juniper (Juniperus communis L.)
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abstract
Juniper (Juniper communis L.) berries are widely used in different products such as perfumes,
pharmaceuticals and to aromatize alcoholic beverages. In particular, they are employed with other
botanical ingredients in the production of commonly consumed juniper-based spirits, such as gin [1].
Juniper berries are also frequently used in the European gastronomy to season and flavour foods, being
considered the only spice obtained from Cupressaceae plants and one of the few examples of spices
produced in cold or temperate regions [2]. In the northeast region of Portugal, the berries are traditionally
used in game meat dishes. Besides being used in drinks and for culinary purposes, J. communis berries
are also used in folk medicine for their diuretic, antiseptic, stomachic, and carminative properties [3],
being inscribed in different Pharmacopoeias.
In this work, the total content of phenolic compounds and of flavonoids, reducing power and antioxidant
activity (in vitro measurement of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity) of
the methanolic extracts of juniper (Juniperus communis L.) berries and leaves were evaluated using
spectrophotometric techniques. Two samples of berries were acquired in a local supermarket and in a
specialized store, respectively and one sample of berries and leaves were collected in the wild in Trásos-
Montes region. Additionally, the antimicrobial activity of a sample of essential oil obtained by
hydrodistillation was determined by the macrodillution broth assay against several Gram-positive and
Gram-negative bacteria and Candida albicans.
Total phenolics content, determined by the Folin-Ciocalteu methodology and expressed as mg gallic
acid equivalents per gram of sample (GAE/g), ranged from 11.13±1.33 to 16.16±0.64 mg GAE/g for the
berries samples, being significantly higher for the leaves sample (141.12±9.56 mg GAE/g). As expected,
based on the phytochemicals content determined for the berries and leaves, the leaves showed a higher
reducing power (EC50=0.17±0.00 mg/mL) and antioxidant activity, measured as the ability to decrease
to 50% the DPPH absorbance (EC50= 0.10±0.01 mg/mL) compared to the berries (reducing power
ranging from 2.40±0.04 to 3.48±0.26 mg/mL and antioxidant activity ranging from 1.74±0.04 to
3.84±0.39 mg/mL).
The essential oil was able to inhibit the growth of C. albicans and different bacteria (Bacillus cereus,
Bacillus subtillis, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae and Enterococcus
faecalis) to different extents, while showing no activity against Pseudomonas aeruginosa and Proteus
mirabilis.
