Abstract:
Leucosidea sericea is an evergreen shrub belonging to the Rosaceae family with
previous studies that indicated that L. sericea extracts exhibited strong anti-bacterial
properties against Propionibacterium acnes, showing potential as a cosmeceutical. The
plant is traditionally used as a vermifuge, as an astringent and to treat conjunctivitis.
Commercial production is, however, not possible as no information is available on
cultivation and the effect of external environmental factors such as seasonal variation
on the medicinal properties of the plant. Seasonal variation was investigated and it
was found that significant differences were observed between the anti-acne (P. acnes)
activity of plant material collected in different seasons. The best activity was found in
winter with a mean minimum inhibitory concentration (MIC) of 5.20 mg mL 1 compared
to spring at 26.04 mg mL 1. A 1H NMR-based untargeted metabolomic analysis was
used to determine the differences in the chemical profiles of plant samples collected in
different seasons. Principal component analysis (PCA) showed clear separation of the
seasons and a supervised orthogonal partial least square discriminant analysis (OPLSDA)
was used to determine the compounds that differentiated the spring from the winter
samples. The contribution plot indicated a strong positive association with the NMR
regions from d 1.2–1.6, 3.3–4.1, and 6.8–8.0 ppm indicative of a compound with an
aromatic ring. Different LC-MS analyses were used in conjunction with a compound
database, MAGMa and CSIFingerID, which led to the identification of the compound 2-
(4-ethoxyphenyl)-5,6,7,8-tetramethoxy-4H-1-benzopyran-4-one and also confirmed the
presence of tangeritin, rutin, quercetin glucoside, and kaempferol glucosides as well as
several other compounds previously identified from the plant. This compound similar in structure to the anti-microbial flavonoid tangeritin, was only present in the winter
samples. It is therefore recommended that seasonal variation be closely monitored
during cultivation and commercial harvesting, and that winter is the preferred harvesting
season to obtain the best anti-acne activity.
