How to change font shape in only one column of `tabular` [closed]

Question

As in the title: I'd like to be able to determine specific font for each column in a table. I've found in Wikibooks, that \begin{tabular}{ >{\bfseries}l c >{\itshape}r } will result in a table with 1st column in bold and third one in italics, but unfortunately it doesn't work when I try to use it.

Minimal working example:

\documentclass{book}

\usepackage{setspace}
\usepackage{fontspec}
\usepackage{polyglossia}
\usepackage{indentfirst}
\usepackage{supertabular}

\setmainlanguage{polish}
\setotherlanguage[locale=mashriq]{arabic}
\setromanfont[Mapping=tex-text]{Linux Libertine O}
\newfontfamily\arabicfont[Script=Arabic,Scale=1.9,Mapping=arabicdigits]{Scheherazade}

\begin{document}

\begin{table}[h!]
\centering
\begin{tabular}{lrlr} \\
%\begin{tabular}{ >{\itshape}lr >\{\itshape}lr} \\
\multicolumn{2}{c}{nieokreśony}&\multicolumn{2}{c}{określony} \\
kit\=abun & \textarabic{كِتابٌ} & al-kit\=abu & \textarabic{اَلْكِتابُ} \\
\v samsun & \textarabic{شَمْسٌ} & a\v s-\v samsu & \textarabic{اَلشَّمْسُ} \\
\end{tabular}
\end{table}

\end{document}

When I try to add >{\itshape} (the commented line), I get an error: ! LaTeX Error: Illegal character in array arg.