The bark of Swietenia machrophylla is colored dark red, and it is correlated with the extractives constituents such as phenolic compounds. This study, therefore, aims to investigate extractives from the inner and outer bark of S. machrophylla and their effects to color properties. The results showed that the extractive content in the inner bark was higher than the outer except for hot water solubles. In addition, the polyphenols and sugar levels from inner to outer bark were increased, except in the soluble-sugar of hot water extractive. The highest correlation between the absorbance of methanol, hot water-soluble extracts, and total polyphenols were observed using the visual spectrophotometer. The extractives that contributed to the bark's color were indicated from flavonoids with a precursor such as monophenol of catechol and resorcinol.

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Caesalpinia sappan is a shrubby Leguminosae tree commonly found in Indonesia, traditionally utilized as natural dye and herbal drink. However, in the making of traditional herbal drink, the bark is often discarded as residues. This research aimed to investigate total phenolic (TPC), flavonoid (TFC), and tannin (TTC) content as well as the antioxidant activity (DPPH scavenging activity) of the bark successive extracted with n-hexane, ethyl acetate, methanol, and hot water as well as analyzed it with GC-MS. The result showed the highest amount of TPC (824.16±62.28 mg GAE/g), TFC (185.03±1.91 mg QE/g), and TTC (987.07±30.98 mg TAE/g) in the methanol extract of the bark. GC-MS analysis resulted hydroquinone as a major constituent in the methanol extract. Further, antioxidant activity was found the strongest on methanol extract (IC50=63.48), while correlation between antioxidant activity and TFC was found the highest (R2=0.93). These findings suggest that bark of C. sappan is a suitable source of natural antioxidant with strong activity to DPPH radical.

The major function of bark in trees is to protect the living tissues. This is due to the chemical extractives in the bark such as polyphenols and terpenoids. In Indonesia, the bark of Pinus merkusii is of high economic value due to its use in the production of wood and oleoresins. Also, the presence of polyphenols in its bark has the potential of being used as antioxidant agents. Based on this, the aim of this study was to investigate antioxidant activity from the methanol extract of P. merkusii bark. This methanol extract of P. merkusii was subjected to gas chromatography mass spectrometric (GC-MS) method and antioxidant activity assay using 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. The GC-MS analysis showed that the extract sample contained phenolics and sugars as minor compounds with fatty acids and alcohols as major components. The antioxidant activity (IC50) of the sample was 1452.8 ± 208 μg/mL, which could be as a result of the presence of phenolic compounds, fatty acids and alcohols, as well as steroids and alkaloid in it.

Pinus merkusii is the only species in the Pinaceae family to grow in Southeast Asia, including Indonesia, and serves as a source of wood and oleoresins. During the utilization of this pine, the bark is discarded as residue, however, this residue is possibly a potential source of antifungal and antioxidant agents, due to the polyphenol contents. This study, therefore, aims to investigate the antifungal and antioxidant compounds present in the bark of P. merkusii. The ethyl acetate extracts of Pinus merkusii were fractionated to obtain five fractions (Fr. A- Fr. E) and the bioactivity of each fraction was observed. Subsequently, the growth inhibition against Phanerochaete chrysosporium, was evaluated for antifungal activity, while DPPH (1,1-diphenyl-2-picrylhydrazyl) method was used to ascertain antioxidant activity. According to the GC-MS analysis, the ethyl acetate fractions contain triterpenoids and steroids as the dominant compounds as well as minor amounts of mono-sesquiterpenoids and hydrocarbons. The highest growth inhibition exhibited by Fr. C- Fr. E (>60%) indicates triterpenoids and steroids act as a fungal inhibitors. Meanwhile, the five fractions exhibited low antioxidant activity because the steroids and triterpenoids present are possibly ineffective DPPH inhibitors. Also, the antifungal and antioxidant activity R2 values were discovered to correlate 0.3, indicating a low positive correlation.